Satan's Robot was a fictional character in the holographic sci-fi serials The Adventures of Captain Proton, written by Tom Paris. Characters and events in the holonovel were inspired by 1930s American culture, and the robot was typical of the period. It was part of Doctor Chaotica's evil forces, described by Chaotica as "the most evil force in the galaxy." The final chapter of the program was entitled "Satan's Robot Conquers the World."
In early 2375, Tom Paris began playing the program aboard the USS Voyager. He invited Seven of Nine to take the part of Constance Goodheart, who was taken captive by Satan's Robot. Rather than go along with the program's story, Seven unceremoniously opened an access hatch on the robot and pulled out several electronic components, deactivating it. (VOY: "Night")
Later in that year, Voyager encountered several photonic lifeforms while trapped on a subspace sandbar. They interpreted the Captain Proton program as an actual environment, and Doctor Chaotica began to wage war on the lifeforms, who claimed they were from the "fifth dimension." Satan's Robot was damaged by the aliens, but repaired by Tom Paris and Tuvok. It told them of the conflict between Chaotica and the lifeforms, and tried to help the crew to stop Chaotica from using his holographic weaponry on the lifeforms and to free Voyager in the process. Paris, who was under stress due to the situation, swore that once he restore holodeck controls he was going to delete the robot. (VOY: "Bride of Chaotica!")
Background information Edit
The character was heavily influenced by a robot used in several Republic serials from the 1930s to the 1950s including Undersea Kingdom (1936), Mysterious Doctor Satan (1940) (also known as Dr. Satan's Robot) and Commando Cody: Sky Marshal of the Universe (1953). His most famous appearance is in the 1952 film serial Zombies of the Stratosphere, where he battles a Captain Proton-like hero named Commando Cody. Leonard Nimoy played the Martian invader Narab in the serial.
The costume for Satan's robot was created by Michael Hood of Precision Effects, Ltd., who also created various other special effects creature and character costume assets, including the Devidians for the Star Trek: The Next Generation episodes "Time's Arrow" and "Time's Arrow, Part II", the Borg, and the Cardassian armor. 
The robot was included as part of the Virtual Voyager simulation in the Star Trek: Voyager - Elite Force expansion pack and as a character model in the multiplayer scenario.