This page contains information regarding Star Trek: Lower Decks, and thus may contain spoilers.
He was a close friend of Benzan and his family. Because of this, in 2365 Benzan asked him to transport a family jewel, the Jewel of Thesia, to Yanar, the woman he had been seeing and intended to marry. He agreed, and went to Atlec to deliver it in his ship. Instead, his ship broke down, and accepted help from the Enterprise-D which happened to be close by. He boarded the Enterprise to observe repairs, however, unbeknownst to him, both Benzan's father, Kushell, and Yanar's father, Debin, were after him, believing he had stolen the jewel and impregnated his daughter, respectively. Captain Jean-Luc Picard, aware that releasing Okona to either one of them could cause a war, beamed the parties aboard the Enterprise-D to discuss the matter. Okona declared he would hand himself over to Debin rather than be treated as a thief. Instead, Benzan decided to reveal the truth, exonerating him. (TNG: "The Outrageous Okona")
By 2381, Okona worked as a DJ, and was hired to work the Command Conference afterparty on Starbase 25 that year. Following the arrival of Captain Carol Freeman, who was denied entry to the party by the bouncer, she saw Captain John Anderson at the top of the stairs and attempted to get his attention. Anderson, who ignored Freeman, instead focused his attention on Okona, greeting him. Upon learning he was the DJ, she exclaimed, "What? He's not even Starfleet! This is outrageous!" During his performance, Okona wore an eyepatch over his left eye. (LD: "An Embarrassment Of Dooplers")
Okona was played by William O. Campbell.
For the character, the script described: "He has the look of a hero, the twinkle in the steely blue eyes softening the rugged handsomeness of the man." His "heroic visage" further described that "He is dressed in a loose-fitting, open-necked blouse, wide belt and casual looking pants, his look is in opposition to the well-tailored Enterprise crewmembers. His sidearms are also less sophisticated and are tucked into his waistband."
Okona is one of several non-regular characters to lend his name to the title of an episode. The other characters thus honored are Charles Evans, Miri, Elaan, Harcourt Fenton Mudd, Ari bn Bem, Q, Ro Laren, Sarek, Melora Pazlar, Shakaar Edon, Morn, Doctor Chaotica, Ma'Bor Jetrel, Tuvix, Rajiin, Su'Kal, Ephraim, Dot, Edward Larkin, and Kayshon.
In the Myriad Universes story, "The Embrace of Cold Architects," in a universe where Picard is killed when the Enterprise destroys the invading Borg cube with its deflector dish weapon, Captain Riker recruited Thadiun Okona to take over hosting duties in Ten Forward after Guinan elects to leave the Enterprise.
The novel Collateral Damage features Okona in a primary role where it's revealed at some point in the 2380s, he became an agent of Starfleet Intelligence. By the year 2386, Agent Okona worked as a field operative under Lieutenant Commander Sam Lavelle, formerly of the Enterprise-D, and Lieutenant Naomi Wildman. During an assignment to stop Nausicaan terrorists who had acquired a Husnock superweapon, Okona was captured by the crew of the USS Enterprise-E and did not reveal his work with Starfleet Intelligence. After acting captain Commander Worf found a diplomatic solution with the Nausicaan leader Kinogar, Enterprise-E security chief Lieutenant Aneta Šmrhová engaged in a tryst with Agent Okona.
Okona's mirror universe counterpart appears in the second issue of the comic Star Trek: The Mirror War, where he was a thief who went by the nickname "The Obnoxious Okona" and carried out a heist on Tyraeus II. There, he stole some dilithium and other valuables from Terran Imperial Starfleet Captain Jean-Luc Picard of the ISS Enterprise-D. Okona left a note for Picard and his crew. Unfortunately, Picard and his crew caught up with Okona at his cache in the Chandler Asteroid Belt. He was sealed in his storehouse as Commander William T. Riker destroyed his shuttle.