Commander Kruge was a male Klingon officer of the 23rd century Klingon Empire. In 2285, he commanded a Klingon Bird-of-Prey. He was romantically involved with Valkris and kept a "Klingon monster dog" as a pet.
In 2285, Kruge played a major role in a plot to obtain intelligence on the Genesis Device, a Federation technology designed to instantly terraform an entire planet. He saw it as an incredibly powerful weapon, and sought to bring that technology to the Empire. He recruited Valkris as a spy to obtain material from the project, and once successful, she made a rendezvous with Kruge on the Merchantman. When he learned from her that she had viewed the material even though she was not to have done so, he destroyed the vessel without beaming her aboard.
Kruge, now with the project summary in hand, ordered a course set for the Genesis Planet, which had only recently been formed. Arriving at that destination, he and his crew encountered the USS Grissom, a Federation science vessel assigned to study the planet. Kruge wanted to gain hostages with which to bargain for the Genesis technology, so he ordered his gunner to target the Grissom's engines in order to disable the vessel. However, in what the gunner described as a "lucky shot," the Grissom was destroyed. Kruge responded by instantly killing the gunner. After Torg found that a landing party from the Grissom had survived on the planet's surface, Kruge led a team to search for them.
Searching the surface
Shortly after beaming down to the surface of Genesis, Kruge and his officers had an encounter with some giant worms, one of which momentarily throttled Kruge until he bloodily squeezed the creature to death with his bare hands. He then contacted the Bird-of-Prey to report that their search had been uneventful.
Kruge and his companions eventually located the team they had been seeking, consisting of Starfleet officer Lieutenant Saavik, David Marcus – son of Admiral James T. Kirk – and a rejuvenated Captain Spock, whose body had been inadvertently revived by the effects of the Genesis Device. Taking the team as hostages, Kruge demanded to know the secret of Genesis, and refused to believe Saavik when she informed him that the technology was fundamentally flawed, and that the planet they were on was on the verge of destroying itself.
Encounter with the Enterprise
Upon the arrival of Admiral Kirk and the USS Enterprise, Kruge returned to his ship and attempted to ambush the Federation vessel. The Enterprise crew detected the Bird-of-Prey's cloaked approach and preemptively fired a pair of photon torpedoes at the now visible Klingon ship, causing the death of Kruge's monster dog. An enraged Kruge returned fire with a torpedo, expecting to be destroyed because the Federation craft outgunned him ten to one. He was meanwhile unaware that the Enterprise was crewed only by Kirk and a handful of bridge officers. Without its normal crew of hundreds, the Enterprise was effectively disabled when Kruge's torpedo knocked out its automation center. Kirk, bluffing, opened communications to demand Kruge's surrender.
Sensing that Kirk was hiding something, Kruge instead ordered Kirk's surrender, threatening to execute the prisoners as "enemies of galactic peace." As proof of his commitment, Kruge ordered his men on the surface to choose at random and kill one of the prisoners. One of Kruge's men moved to stab Saavik, but David immediately intervened, sacrificing his own life to save her. In response, Kirk deceived Kruge into believing that he was indeed surrendering, allowing a Klingon team aboard the Enterprise while he and his own crew surreptitiously set the ship's auto-destruct and beamed down to the planet.
The final confrontation
After the destruction of the Enterprise and the death of the bulk of Kruge's crew, Kirk contacted him from the surface, demanding to be beamed up. Kruge, however, chose to beam down himself to confront Kirk, allowing the rest of his crew to transport to the Bird-of-Prey.
Kruge then engaged in a fight with Kirk, amid the conflagration of the dying Genesis planet, but lost his footing as the ground gave way beneath him, leaving him clinging to the edge of a cliff. Kirk offered to pull Kruge up from the precipice he was hanging from, but instead of accepting Kirk's offer of mercy, he attempted to yank them both to their deaths. He failed, and was left dangling from Kirk's foot over an immense lava flow. Kirk then kicked him in the face three times, causing him to fall into the inferno to die. (Star Trek III: The Search for Spock)
Kruge was played by actor Christopher Lloyd.
Developing the character
While the antagonists in Star Trek III were originally to have been Romulans, this character was likewise thought of as a Romulan, the unnamed commander of a Romulan Bird-of-Prey. He was depicted that way in a story treatment called Star Trek III: Return to Genesis, written by Harve Bennett and dated 16 September 1982. In that story outline, he was initially described thus; "The Commander is a handsome, swarthy man with a dignity reminiscent of the 20th Century actor Omar Sharif. Like all Romulans, he is physically similar to Vulcans, his brother race. The sharp pointed ears... the tilted brows. But unlike the more highly evolved Vulcan civilization, cool and dedicated to logic, the Romulan is of blood and passion. His mission is intelligence. He is Captain of a spy ship." At the end of the story, the Romulan commander, stranded alone on the disintegrating Genesis planet, with Kirk and his crew having commandeered the Bird-of-Prey, was contacted by Kirk and offered a chance to escape. However, he declined, choosing to be doomed together with the Genesis planet. (Star Trek: The Magazine Volume 3, Issue 8, p. 30)
Kruge wasn't named until the writing of the film's screenplay, in which he was referred to as a "Battle Commander". In the stage directions from the first draft of the script, he was initially characterized thus; "Battle Commander Kruge is tall, dark, and universally attractive. Some of that comes from his arrogance, his relative youth and, by Klingon standards, his charm. He is a deadly swashbuckler." This version of the script (dated 23 March 1983) did not include Kruge's romantic connection and killing of Valkris (as her character was yet to be invented). Instead, at the start of the story, Kruge was absent from a flotilla of Klingon battle cruisers, leading his superiors, who were in command of those ships, to wonder where he was. He then decloaked in a Romulan Bird-of-Prey amidst the flotilla, having somehow managed to commandeer that ship. His abrupt arrival in a Romulan vehicle completely surprised the assembled Klingons. ("Space Docks and Birds of Prey", Star Trek III: The Search for Spock (Special Edition) DVD & Star Trek III: The Search for Spock (BD) special features) Just before leaving the Bird-of-Prey's bridge, he made a joke which implied that he and his crew had served time in prison. Already having the Genesis demonstration tape with him, Kruge proceeded to convince the Klingon council of war to assign him, his officers, and a mysterious spy named Galt to investigate the secret of Genesis and travel, aboard the Romulan craft, to the Genesis planet. During his encounter with large serpentine creatures there, Kruge demonstrated to his second officer, who had been about to shoot the serpents, that it felt better to instead kill them by crushing them with one's own bare hands. At the end of the script, Kruge was killed by Kirk throwing, into his back, the same Klingon dagger which had been used to murder David Marcus.
The writers decided to have Kruge kill Valkris as a way to impart to the audience that the Klingon species was extremely ruthless. (audio commentary, Star Trek III: The Search for Spock (Special Edition) DVD & Star Trek III: The Search for Spock (BD) special features) In the revised final draft of the script (dated 7 October 1983), he was portrayed in much the same way as he is in the final version of the movie, including his involvement with Valkris, and his death scene. Kruge was initially described, in this draft's stage directions, as "a Klingon War Lord of handsome but frightening presence, and relative youth." The reference to him as a "Klingon War Lord" explains why Saavik, Valkris, and his crew refer to him in the film as "my Lord." Additionally, he was still referred to as a "Battle Commander" in the script. 
Ever since he first read the screenplay for Star Trek III, Kirk actor William Shatner was impressed by the writing of the Kruge character. In the Shatner and Chris Kreski book Star Trek Movie Memories (hardcover ed., pp. 159-160), Shatner remembered, "I liked Kruge, our over-the-top gung-ho/psycho Klingon power junkie, a lot."
Casting the role
Prior to Christopher Lloyd being cast as Kruge, many candidates tried out for the part. (Star Trek Movie Memories, hardcover ed., p. 168; I Am Spock, hardcover ed., p. 226) Leonard Nimoy, who directed and starred in Star Trek III: The Search for Spock, described the task of casting the role of the Klingon commander as "the biggest issue we had on III." He and Harve Bennett discussed a lot of people who might fit the part. (Star Trek Movie Memories, hardcover ed., p. 168) Nimoy and Bennett also auditioned many actors for the job, although it kept seeming as though those auditionees didn't do the role justice. (I Am Spock, hardcover ed., p. 226; Star Trek Movie Memories, hardcover ed., p. 168) Nimoy recollected, "When they read the part, it just didn't seem to come to life. It didn't work. They just couldn't grasp the character somehow." (Star Trek Movie Memories, hardcover ed., p. 168)
One day, Leonard Nimoy discovered a tape of actor Edward James Olmos (who later found fame as William Adama in Battlestar Galactica) and formed the belief that he would be the perfect choice to play Kruge. (I Am Spock, hardcover ed., p. 226) Nimoy showed the tape of Olmos, who was meanwhile seeking work, to Harve Bennett. "So, Harve watched the tape," continued Nimoy, "and his response was, 'Well, he's not bad, but he's small, a quarterback. I think what we need in this role is a defensive tackle.' I said 'Well, that may be, but let's bring him in, and find out.'" (Star Trek Movie Memories, hardcover ed., p. 168)
Subsequently, Leonard Nimoy invited Edward James Olmos to meet him at Nimoy's house on a Sunday. Nimoy asked Harve Bennett to come, too, but Bennett declined, for reasons unknown to Nimoy. "He told me, 'You make the call, I'll be guided by your judgement,'" recalled Nimoy. "So I saw Eddie and [...] I [still] felt he would do a terrific job. I felt that we could skirt the issue of his size." This was because, for most of the film, Kruge would be sitting alone in his command chair on the bridge of the Klingon vessel, so the only time the production personnel would have to fake the actor's body size would be during Kruge's actual face-to-face confrontation with Kirk. Nimoy even reckoned that, by using creative camera work and elevating the actor on boxes, faking the actor's physical stature would be fairly easy. "Before the day was over, I had more or less committed to Eddie," Nimoy related, "and as we said good-bye I told him, 'This is gonna be great.'" (Star Trek Movie Memories, hardcover ed., p. 168)
However, as Leonard Nimoy found thereafter, Harve Bennett was insistent that Edward James Olmos didn't have the right build for the role. (I Am Spock, hardcover ed., p. 226) Addressing Bennett's concerns that the character had to seem much larger than Kirk and extremely threatening, Nimoy admitted that he concurred and felt sure they could achieve that on screen, with Olmos in the role. Bennett and Nimoy proceeded to debate the issue without making any more substantial progress. Eventually, Bennett suggested they could have Olmos visit the studio and audition for the part there. Nimoy complained that he himself had already auditioned the actor and that Bennett had agreed to trust Nimoy's judgement of Olmos. Bennett responded that he was uncertain if he could persuade the studio executives based on only that. Nimoy was starting to feel awkward about the prospect of retesting Olmos for a part he had already been notified Nimoy wanted him to perform. Nonetheless, doing as Bennett proposed, Olmos was next interviewed by him at the studio. As Nimoy viewed it, the audition went so well that Bennett wouldn't be able to deny that Olmos would be ideal to play Kruge. Instead, Bennett asked Olmos to come back later and read for the part one last time, this time with a "management person" who Bennett didn't name. The mystery staff member turned out to be Gary Nardino, who had been given the production credit "executive producer" for Star Trek III. Even though Nimoy was shocked by the actor he'd suggested being asked to attend so many interviews, Nimoy, as a first-time director, didn't know what his limitations were and consequently was afraid of taking a stand, in case he lost the privilege to direct the film. (Star Trek Movie Memories, hardcover ed., pp. 168-169)
With Gary Nardino now present, Edward James Olmos again auditioned. "By the time he'd finished and left the room, I knew he was dead," Leonard Nimoy lamented. "Nardino said, 'I don't get it at all. To me, this is a character who should be 'to the manor born.' He's a sophisticated, Terence Stamp kind of guy.' I said, 'I don't think that at all. I think he's a bright, intense, gung-ho, threatening kind of bad guy.' But for all intents and purposes, it was now two against one, and Eddie was gone." (Star Trek Movie Memories, hardcover ed., p. 169)
The disagreement between Leonard Nimoy and Harve Bennett was ended when Christopher Lloyd expressed interest in playing Kruge. "Harve Bennett and I couldn't be dissuaded; when Lloyd indicated he wanted the role, we deemed ourselves lucky to get him," Nimoy explained. (I Am Spock, hardcover ed., p. 226) Lloyd came in to be interviewed for the job; he auditioned for Nimoy. (audio commentary & "Captain's Log", Star Trek III: The Search for Spock (Special Edition) DVD & Star Trek III: The Search for Spock (BD) special features) The director noted, "Chris came to my office, and he read a little bit of the part for me." (Starlog, issue 219, p. 48) Since Lloyd wasn't yet established as a major movie actor, it wasn't a forgone conclusion that he would win the part. There was even some worry at the studio that Lloyd would be seen as too funny an actor to portray Kruge, as he was used to appearing in a regular comedic role in series television and the studio wasn't sure if he could play a far different character. "There was some concern [....] Could he be this commanding authority figure that Kruge had to be?" recalled Nimoy. (Star Trek: The Magazine Volume 3, Issue 8, pp. 17-18) Despite Nimoy having admired Lloyd for years prior to the making of Star Trek III, the audition amazed Nimoy. "What he really did for me when he came in," he said about Lloyd, "was show me how totally chameleon-like he is. When he came in and read this role, he was totally unlike anything I'd ever seen him do before, and I was just swept away by his ability to transform himself so completely and to give us this wonderful, powerful character, and I went to bat to hire him on the spot." (audio commentary, Star Trek III: The Search for Spock (Special Edition) DVD & Star Trek III: The Search for Spock (BD) special features) Specifically, Nimoy – who had overcome typecasting issues himself, having become famous in the role of Spock – expressed to Harve Bennett that Lloyd was the right man for the job. "I went to Harve Bennett's office," Nimoy recounted, "and I said, 'He's a chameleon. He can do it.'" Nimoy also gave assurances that, if Lloyd was cast in the role, it would work. ("Captain's Log", Star Trek III: The Search for Spock (Special Edition) DVD & Star Trek III: The Search for Spock (BD) special features)
Regarding how his name came up for the role, Christopher Lloyd wasn't entirely sure. "I guess, well, maybe it's because Leonard Nimoy has a great deal of respect for actors," Lloyd hypothesized. "He has a theatre background. He may have felt he needed people well grounded as actors to make the Klingons work." When the part was offered to Lloyd, he was surprised. "I was honored. Really, I was tickled and delighted," he reminisced. "What can I say? I felt like I was becoming part of a special club." (Starlog, issue 82, pp. 20-21) Lloyd was unsure what the film's production staffers had seen in his previous work that had convinced them he might be good at adopting the role of a Klingon.  However, he speculated that, by casting him in the role, "they just played a hunch, I guess."  As Robin Curtis observed, Lloyd, rather than having to learn all the nuances of details about his character, approached the role of Kruge simply by acting. (Star Trek Monthly issue 6, p. 50) The part did, though, challenge him to learn Klingonese. Lloyd struggled to learn the language, but, with help from Leonard Nimoy and linguist Marc Okrand, he enthusiastically endeavored to make Kruge's uses of Klingonese as accurate as possible. (Starlog, issue 82, p. 21; "Speaking Klingon", Star Trek III: The Search for Spock (Special Edition) DVD & Star Trek III: The Search for Spock (BD) special features)
Filming the character
As the director of Star Trek III: The Search for Spock, Leonard Nimoy tried to accentuate how menacing Kruge looked, such as by using tight angles on the bridge of his Bird-of-Prey. Although Nimoy tried to use that method for the ship's Klingon crew in general, he was especially mindful of it in relation to their commander. "And the fact that he was elevated above them in the way he was gave him a certain amount of ominous power," Nimoy pointed out. (Star Trek: The Magazine Volume 3, Issue 8, p. 16)
Christopher Lloyd thoroughly enjoyed playing Kruge. Describing the Klingon years after playing him, Lloyd said, "It was fun to play an evil character that has no remorse about anything he does [....] I love doing that kind of thing, a far-out character."  The actor elaborated, "I mean, he epitomizes somebody with absolutely no moral conscience. He even blows up his so-called girlfriend in another spaceship. They have a short conversation at the beginning, and he doesn't even apologize. She's amenable because… well, it's for whatever political reasons. But, yeah, he's just evil [....] He's demonic. There's no conscience in place at any point, and he has no apologies for any of his actions. He just goes out and destroys and kills and creates havoc until he gets what he wants. And that was fun to play. I loved all the makeup and the clothes, the whole Klingon look. It was a joy."  Reminiscing, Lloyd noted, "There were certain moments I remember when I shot them that I felt I'd captured the character well." ("Captain's Log", Star Trek III: The Search for Spock (Special Edition) DVD & Star Trek III: The Search for Spock (BD) special features)
Although Christopher Lloyd and Chekov actor Walter Koenig had been schoolmates in their childhood, Koenig found that, during the making of Star Trek III, Lloyd's focus on playing Kruge took priority. "He was very much into his character, which was good, but he was not very approachable as a consequence," Koenig noted. Deborah Arakelian, assistant to Harve Bennett, remembered, "Chris Lloyd [...] would sit there in full makeup with his little wire glasses on, reading the trades [....] It was pretty funny to look at. He had almost no interaction with anyone. Came in and did his job, such a professional." Eddie Egan, who was working in the publicity department at Paramount Pictures when the film was being marketed, recollected, "I think he just felt very out of place. There were whole parts in the movie where he didn't interact with any of them until the end except with Robin Curtis and Merritt Butrick [who played Saavik and David Marcus respectively]. No one likes wearing that kind of makeup in that kind of heat for that many hours a day. It was a very quick job. He didn't work that long." (The Fifty-Year Mission: The First 25 Years) Concerning the Klingon make-up, Maltz actor John Larroquette attested that Lloyd had a particularly difficult time dealing with it, Larroquette stating, "He sweated quite a bit. They had to keep poking his makeup with holes so they could squeeze the sweat out." As far as Larroquette saw, though, Lloyd didn't take the making of the movie too seriously, and Larroquette later joked, "At some point in the film, I wanted Christopher Lloyd to turn to me and say, 'Bring me some chocolate, Maltz.'" (Starlog, issue 138, p. 25)
Upon considering how to film the scene in which Kruge is attacked by massive worms, the production crew were careful not to ruin Kruge's make-up. This prohibited them from doing multiple takes of the worms leaping on him, as the members of the film crew were anxious that shooting too many takes would eventually mess up the prosthetics Christopher Lloyd needed to wear for the role. Even so, during the actual filming, his elaborate Klingon costume kept snagging on fishing line that the team used to make the rubber worms appear to be moving. For a close-up insert shot of Kruge grabbing the worm that then attacks him, Industrial Light & Magic effects cameraman Don Dow stood in for Lloyd, and the shot was captured at ILM. (Cinefex, No. 18, pp. 55 & 56)
Christopher Lloyd had a problem with performing the scene where Kruge, having just learned the Enterprise has arrived in proximity of the Genesis Planet, calls his Bird-of-Prey in order to be beamed back aboard. Lloyd's issue with the scene, namely using the prop of the Klingon commander's communicator, meant multiple takes of the scene had to be shot. Despite Leonard Nimoy giving Lloyd several reminders to speak into the prop when ordering that he be beamed up, Lloyd persistently didn't do so and instead kept stretching his arms out wide and shouting the command to the heavens. With a laugh, Robin Curtis later mused, "It was just so interesting that he didn't need to be anchored that way to his character [....] He [...] certainly didn't need a prop to get him up on a ship, you know; he could be beamed up without the communicator!" ("Captain's Log", Star Trek III: The Search for Spock (Special Edition) DVD & Star Trek III: The Search for Spock (BD) special features)
Visualizing Kruge's demise
There was absolutely no way, of course, that the scene in which Kruge falls from a precipice on the Genesis Planet could be depicted by throwing an actor over the edge of a cliff into a sea of burning lava. (Star Trek: The Magazine Volume 3, Issue 8, p. 111) Instead, a performer was filmed taking a short drop into an airbag. (Cinefex, No. 18, pp. 63 & 64) According to Cinefex (No. 18, p. 63), this live-action performer was a stuntman. However, according to Star Trek: The Magazine Volume 3, Issue 8, p. 111, the performer was Christopher Lloyd himself, a claim which seems supported by a statement he made. 
At ILM, David Sosalla and Tom St. Armand were called upon to enact Kruge's final fate. In Sosalla's opinion, Kruge tumbling to his death made him seem "sort of like Wile E. Coyote." (Cinefex, No. 18, p. 64)
The shot was to be completed with an articulated stop-motion puppet visually substituting the performer, seamlessly, midway through the plunge. (Cinefex, No. 18, pp. 63 & 64) However, the live-action footage complicated the puppet's requirements. "The problem was that the cut we were given of Kruge going over the cliff was so short that at the end of it he was still large in the frame," explained David Sosalla. "We had to meticulously copy the images, picking up where Kruge is kicked off, and still have it hold up under scrutiny of being half-size on screen. That's pretty hard for a little puppet." (Cinefex, No. 18, p. 64)
The puppet was sculpted by David Sosalla and crafted by Sean Casey. Tom St. Armand designed a special armature for the puppet. (Cinefex, No. 18, p. 64) To begin the sculpting process, a clay maquette of Kruge was sculpted. "Then we created all the molds using that clay maquette, and inside that we put the armature, which is like a skeleton; there were joints for the elbows, the knees, the hips, all the way through the body, and even the backbone," Sosalla explained. "That was cast into foam rubber from that mold. Then we took it and dressed it. We painted it with flexible paint." The highly detailed puppet was made to a quarter scale. (Star Trek: The Magazine Volume 3, Issue 8, p. 111)
Once the puppet was finished, it was filmed with a technique that Sosalla called "stop-go motion," which combined traditional stop motion and a model mover that could add a motion blur to the footage of the puppet. The filming involved running the camera for a single frame, and then having the puppet's limbs be very subtly moved by an animator prior to shooting the next frame. The movements had to be exceptionally smooth, so the puppeteer needed to be able to access the puppet's joints. That was facilitated by the existence of adjusting screws on every joint. (Star Trek: The Magazine Volume 3, Issue 8, p. 111) The movements were programmed by Denis Muren, with Tom St. Armand animating the puppet when it was filmed against bluescreen. (Cinefex, No. 18, pp. 63 & 64) "After the model was cast, depending on who the animator was," continued David Sosalla, "we'd cut little slits into the foam so they could go in and adjust the joints after casting was made." The puppet was then matched up very precisely with the footage of the live-action performer and, at a suitable moment, was used to replace him. (Star Trek: The Magazine Volume 3, Issue 8, p. 111) The transition was covered with an animated lightning flash, helping make the illusion look convincing. (Cinefex, No. 18, p. 64)
Although the puppet only appears fleetingly in the movie, filming the puppet took about two days. (Star Trek: The Magazine Volume 3, Issue 8, p. 111) David Sosalla was of the belief that that duration was worthwhile. "It wasn't a huge puppet, but it held up magnificently under close scrutiny," he remarked. (Cinefex, No. 18, p. 64) Christopher Lloyd was similarly proud of how Kruge's demise was ultimately depicted, the actor enthusing, "I thought it was a great ending for the character, very entertaining. And I couldn't tell where I ended and the puppet started." 
Christopher Lloyd was hopeful that his performance of Kruge would be popular. Shortly before Star Trek III: The Search for Spock was released, he admitted, "I like to think that whatever I did in the film fulfills the Trekkian hopes. Know what I mean? I'm thrilled thinking that somehow I've contributed to the whole Trekkian mystique." (Starlog, issue 82, p. 20) Lloyd himself had mixed feelings about his work in the film. With a discerning eye to his presentation of the character, Lloyd conceded, decades after playing Kruge, "There's always a couple of moments here and there where I feel I could've been sharper, I could have been more clear. But [...] when I see the film [...] over the years, I still feel, yeah, I did that, I got that. And there are some moments that I feel, if I had to do them again, I feel I could improve upon them, but that's with everything." ("Captain's Log", Star Trek III: The Search for Spock (Special Edition) DVD & Star Trek III: The Search for Spock (BD) special features)
Leonard Nimoy found that Christopher Lloyd was very helpful in making Kruge seem larger than life; in Nimoy's opinion, Lloyd played the role "brilliantly," defying the studio concerns that he wouldn't be capable of the assignment. (audio commentary, Star Trek III: The Search for Spock (Special Edition) DVD & Star Trek III: The Search for Spock (BD) special features; Star Trek: The Magazine Volume 3, Issue 8, p. 18) "I thought he brought a tremendous amount of theatricality to the character of the Klingon," Nimoy opined. (audio commentary, Star Trek III: The Search for Spock (Special Edition) DVD & Star Trek III: The Search for Spock (BD) special features) He elaborated about Lloyd, "His portrayal of Kruge was a joy to watch; he literally smacked his lips as though savoring the role. It made me happier than ever to be working with Klingons!" (I Am Spock, hardcover ed., p. 226) Nimoy clarified, "He was wonderful to work with and wonderful on film. He brought the power and the authority to it that it needed, the intensity that it needed, and did it very, very well." ("Captain's Log", Star Trek III: The Search for Spock (Special Edition) DVD & Star Trek III: The Search for Spock (BD) special features)
Other members of the Star Trek III shooting company have likewise been complimentary about Christopher Lloyd's portrayal of Kruge. For example, William Shatner believed that Lloyd strengthened the principal cast. "Hidden under gobs of makeup and one of those patented Klingon headpieces that always look sort of like big bronze omelets, Lloyd was almost entirely unrecognizable [...] and he chewed the scenery with a tremendous amount of skill and enthusiasm (even going so far as to become fluent in the formal Klingonese language) [....] He quickly grew more comfortable [...] in his role," observed Shatner and Chris Kreski. (Star Trek Movie Memories, hardcover ed., pp. 173-174) In admiration of Lloyd's "visceral" portrayal of Kruge, Robin Curtis remarked that watching him work had been a great pleasure. ("Captain's Log", Star Trek III: The Search for Spock (Special Edition) DVD & Star Trek III: The Search for Spock (BD) special features) Marc Okrand was happy with how Lloyd handled the Klingonese in Star Trek III, commenting, "He did an incredible job." ("Speaking Klingon", Star Trek III: The Search for Spock (Special Edition) DVD & Star Trek III: The Search for Spock (BD) special features) A more mixed opinion was voiced by Sarek actor Mark Lenard, who commented, "Christopher Lloyd was entertaining in Trek III, though I suspect playing a Klingon is more serious business than he made it." (Starlog, issue #138, p. 35)
Todd Bryant, who later played Klaa in Star Trek V: The Final Frontier, was a fan of Kruge even before being cast as Klaa. "I loved Christopher Lloyd's role as Kruge," he remarked. (Starlog, issue #149, p. 63) Ronald D. Moore and Michael Taylor, who worked on some of the Star Trek spin-off series, were approving of the characterization of Kruge but were uncertain as to why Lloyd, primarily known as a comedic actor, had been cast in the part. Taylor enthused, "Christopher Lloyd was actually a pretty damn good Klingon." He also considered it "kind of cool" that, at one point, Kruge picks up and kills a massive, dangerous worm just so he can then report that nothing noteworthy has been happening. Additionally, Taylor thought highly of the way the character talks with Kirk, just after their brief space battle. "I do kind of like the way that he can turn the sabre rattling, you know," Taylor commented, "and this whole political invective against him. And say, 'Hey, we're not the bad guys here. You're the guys creating ultimate weapons and stuff like that.'" Moore, for his part, liked when Kruge refuses Kirk's help and is then killed in retaliation, describing it as "the best part" of the climactic fight scene between them and referring to Kruge's fall as "cool." (audio commentary, Star Trek III: The Search for Spock (Blu-ray) special features) On the other hand, Star Trek: Enterprise writing staffer David A. Goodman critiqued, "I thought Christopher Lloyd didn't feel like a Klingon to me." (The Fifty-Year Mission: The First 25 Years) In 2009, John Eaves characterized Kruge as "legendary" and suspected that Edward James Olmos wouldn't have been able to pull off the part, speculating, "Back then I don't think he would have had the grit to really make that role work. He was pretty skinny then too. Today he would be an awesome Kruge."  
Writing duo Kevin Dilmore and Dayton Ward called Kruge "little more than [a] moustache-twirling villain." (Star Trek Magazine issue 151, p. 31) Writer Lance Parkin commented, "Kruge [...] is someone with the super-villain management style that calls for the casual murder of his subordinates, but there's a little more than that to him and the movie does take time to make him at least a little sympathetic." (Star Trek Magazine issue 149, p. 18) Author and journalist Edward Gross contended, "Christopher Lloyd is surprisingly good as a Klingon, bringing serious tension and dark humor at key moments." (Trek Navigator: The Ultimate Guide to the Entire Trek Saga, p. 222)
When Star Trek III was released, Kruge's death proved to be extremely controversial with Star Trek's fanbase, as regards Kirk's morality (or lack thereof) in killing Kruge. (audio commentary, Star Trek III: The Search for Spock (Blu-ray) special features)
Kruge was the first Klingon to be addressed as "my Lord" (though in Star Trek Generations, the word used to address Kruge, "joHwI'", translated as "my lord", is used to address the Duras sisters by their crew). Later, Kol was addressed as "my Lord" in episodes of Star Trek: Discovery. He was the second Klingon to try and seize control of the Enterprise (the first was Kang in "Day of the Dove"). As noted in the text commentary for Star Trek III, Kruge was also the second Klingon to use hostages to coerce Kirk (that precedent was set by Kor threatening to exterminate scores of Organians in "Errand of Mercy"), and the second Klingon to fall for Kirk's bluffs (preceded by Kang doing so in "Day of the Dove"). Kruge was also the first character to ever be killed in a premeditated way by Kirk, which was why the incident was so controversial with fans. (audio commentary, Star Trek III: The Search for Spock (Blu-ray) special features) In addition, Kruge was the first of numerous Klingons to each be established as having a pet, with others including Klingon guards on Rura Penthe in Star Trek VI: The Undiscovered Country (the owners of a group of jackal mastiffs), Worf in Star Trek: The Next Generation (who kept a targ in his childhood), and Doctor Antaak in Enterprise two-parter "Affliction" and "Divergence" (owner of a targ named Boshar).
Marc Okrand, who invented Klingonese, noted that Kruge is "the main speaker of Klingon" in Star Trek III, the first Star Trek movie which Okrand worked on. Christopher Lloyd's delivery of the Klingon dialogue, therefore, set a standard as to how Klingonese would ideally be spoken. ("Speaking Klingon", Star Trek III: The Search for Spock (Special Edition) DVD & Star Trek III: The Search for Spock (BD) special features) In Okrand's tlhIngan Hol language, Kruge's name is Qugh. (The Klingon Dictionary 2nd ed., p. 58) In an audio commentary for Star Trek III, Michael Taylor joked that Kruge was multilingual, understanding not only English and Klingon but also French, as Kirk at one point says to him, "C'est la vie."
Kruge also originated the term "honor" being associated with Klingon warriors, as he tells Valkris, right before destroying the Merchantman, that she "will be remembered with honor." This line was highly influential to Ronald D. Moore in writing further material for the Klingon species, in later years. (audio commentary, Star Trek III: The Search for Spock (Blu-ray) special features) Despite its historical implications, Kruge's involvement with Valkris wasn't included in all edits of the movie, as the scene was commonly censored from TV versions of the film. (Beyond the Final Frontier, p. 70)
Concerning a moment in the film when Kruge threatens Saavik with torture, Michael and Denise Okuda posited, in the text commentary for Star Trek III, "Kruge seems unaware that Vulcans discipline themselves to control pain." Because sandwich boxes were used to decorate the base of Kruge's command chair, the commentary joked, "He had to step carefully to avoid crushing them!"
Only one shot of Kruge, issuing an order to one of his subordinates in Klingonese, was included in the theatrical trailer for Star Trek III. The scene in which Kruge falls to his demise was shown during a video montage at the end of the Star Trek 25th Anniversary Special, followed by the text "He Boldly Went Where No One Went Before."
In the book The Gospel According to Star Trek: The Original Crew (pp. 118 & 119), author Kevin C. Neece suggested that Kruge metaphorically represents Satan the Devil, with Spock representing Jesus Christ. Pondered Neece, "Kruge [...] is an antichrist. He is arrogant, selfish, and greedy. Where Spock gave up his life to save others, Kruge will take life to further his own desires [....] Unlike Spock's famously nonviolent maneuver, Kruge's neck pinch [exerted on the huge serpentine creature] is lethal. He sees Genesis (the power of creation) as something to be used for personal gain, to bring death and not life. The power of Genesis is supposed to be life from lifelessness, but Kruge sees it as 'the most powerful destructive force' ever known. Kruge wants to steal Genesis, kill anyone who gets in his way, and to destroy with the Genesis device, just as the thief comes in Jesus' words [as stated at John 10:10]. But Christ has come 'that they may have life and have it abundantly' [in other words, to allow other people to 'live long and prosper'] [....] Kruge is so driven by his obsession that he doesn't consider the ineffectiveness of his actions. He is being completely irrational, fighting to the death with the person he wants to give him the knowledge he seeks. He is the anti-Spock." Neece also postulated that Kruge being kicked into a lava pool on Genesis could be seen as analogous of how Revelation 20:10 declares that the ultimate victory over evil will involve the Devil being cast into a fiery pit.
Several licensed action figures bearing Kruge's likeness have been released. An Ertl figure of him – the packaging of which referred to the character merely as "Klingon Leader" – was released in 1984, in a pack that also included his pet beast. That set was in Ertl's Star Trek III: The Search For Spock line, for which Kruge was illustrated as part of the card backing used for packaging all the action figures. In 1983, the prototypes for this range of figures included a very early, rough cast of Kruge, who was to have been packaged with a collie.  In 1995, a Kruge action figure featured in Playmates Toys' Classic Star Trek: The Movies series, though some of these Kruge figures were mistakenly packaged with the Martia card backing. In 1997, Playmates included Kruge as a slightly-bigger-than-an-inch action figure in a set of three Star Trek: Strike Force figures, with a similarly sized Valkris and a much larger Klingon Bird-of-Prey. Two bobble-head dolls of Kruge have also been manufactured; one (made by Bif Bang Pow! and released in 2014) called him "Commander Kruge", whereas the other (by Funko) referred to him as "Captain Kruge". Diamond Select Toys planned to release a Kruge action figure, too, but it was cancelled, without explanation. 
Kruge has also appeared on numerous trading cards. His final fate was pictured on card 26 (called "The End of Kruge") of SkyBox International's The Star Trek Cinema Collection in 1994, and SkyBox also released a face card of Kruge, as card #3DS in the Star Trek - Cinema 2000 range, in the year 2000. Kruge was also the subject of two different trading cards in Decipher's Star Trek Customizable Card Game. One of these, numbered 84R, was part of a series called The Motion Pictures, a set released in 2002. The other, released in 2006 and numbered 11P22, highlighted him as an "Instinctive Commander" and was part of a series named Genesis. Kruge actor Christopher Lloyd was specifically featured on an Autograph Card, numbered A14, in The Complete Star Trek Movies series, produced by Rittenhouse Archives in 2007, and Kruge was the subject of Gold Parallel Base Card #78 in the company's Star Trek Aliens card series in 2014. "Kruge's Bird-of-Prey - B'rel-class card pack", for board game Star Trek: Attack Wing, included a card of Kruge himself as well.
Various other items of Kruge merchandise have been released, too. In 1984, Taco Bell produced a glass tumbler which featured Kruge. It displayed his face, referring to him as "Lord-Kruge", and his final moments, hanging from a precipice, with Kirk offering a hand to pull him up. The same glass also referred to him as "Klingon Battle Commander Kruge". Lastly, Kruge is also featured in the computer game Star Trek Timelines.
A Klingon named Kruge appears in the novel Faces of Fire by Michael Jan Friedman, which takes place several years before the events of Star Trek III: The Search for Spock. It is unclear whether he is the same character as appears in the movie, but the two are strongly similar.
In Star Trek: Prey, it is revealed, that after his death, Kruge's family hired various mercenaries to battle on their behalf as Kruge was the only true warrior in his House, his family possessing great resources but none of them having any true skill at waging a military campaign. Although Kruge had chosen Korgh as his heir, Korgh's status was never made official before Kruge's death, forcing Korgh to spend the next century operating behind the scenes until he was ready to initiate a complex plan to take control of the Klingon Empire, which includes the apparent death of Emperor Kahless at the hands of the Unsung, the descendants of the discommendated soldiers who fought against the rest of Kruge's famiy while acting in his name. In the course of the miniseries, Korgh's goal is confirmed to be to sow discord among the Empire by presenting the Federation as incapable of dealing with their threat and then betraying the Unsung to his own chosen followers, thus increasing his own standing in the Empire. However, despite Korgh's efforts, his plans are thwarted when he underestimates the Federation and overestimates his influence over his 'allies', to the extent that Worf and Kahless are able to win the Unsung to their side. This culminates in Kahless joining the last surviving Unsung to help them regain their lost honor while Korgh is sentenced to Discommendation himself, his remaining direct family joining the High Council in rejecting him after Worf pleads for leniency on their behalf, leaving Korgh to be arrested by Admiral Riker once he is no longer subject to the authority of the Klingon Empire.
- Kruge at StarTrek.com, the official Star Trek website
- Kruge at Memory Beta, the wiki for licensed Star Trek works
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