Tom Servo is the red robot with a clear Pyrex dome on his head on TV's Mystery Science Theater 3000. He was constructed by Joel - both the character, Joel Robinson, and the series creator, Joel Hodgson - from spare parts either littered around the Satellite of Love or around the KTMA studios, depending if you want to believe the series continuity fiction or the actual facts, respectively. While he does not have eyes per se, it is widely believed that his dome serves as some sort of sensory device. Servo is the more realistic of the MST3K 'bots and along with fellow 'bot Crow T. Robot and human captive Joel Robinson (later Mike Nelson) he watches the horrid movies sent by Dr. Clayton Forrester (and later Pearl Forrester). In his earliest incarnation he was silver and known as "Beeper" and could only speak in beeps that his fellow 'bot Crow T. Robot could understand. This concept was abandoned quickly and beep-maker Josh Weinstein began speaking for the robot, now renamed simply "Servo". His first name, Tom, would not be added for several weeks. After the show's first year on Comedy Central Weinstein took off for fame and fortune, allowing show writer Kevin Murphy to step into the role of the stout red automaton. It was under Murphy's performance that Servo gained his profundo voice and bigger-than-life ego. Not all MST3K fans approved of the new characterization, however; one bitter fan sent a large banner to Murphy that read "I HATE TOM SERVO'S NEW VOICE!" which Murphy hung in his office for over a year. Onscreen, Servo developed his new voice after Joel tinkered with his voice modulator in episode #201, Rocketship X-M. He's also the only robot that needs to be carried in the theater due to his hoverskirt's inability to maneuver over the ventilation grate next to his seat (of course, the real reason is that Kevin Murphy is already in position to wield the Servo puppet for the theater segment and the puppet must be handed to him by Joel/Mike).

Servo's exact character is hard to pin down. Nobody gets him ("I'm the wind, baby!" he once told Gypsy when she was trying to figure him out), although he does possess a hell of a singing voice and has been known to turn gentle arias and choral music into randy, raunchy tunes. He's also had his share of get-rich-quick schemes (such as hat distressing, pecan farming, apartment ownership, and so forth), although he's had little luck in this field. Tom is incredibly proud of his prize underwear collection, and in episode #810, The Giant Spider Invasion, he listed the entire contents of the collection (which was previously seen in Mystery Science Theater 3000: The Movie). It consists of...

  • 342 pr Cotton Boxers (no duplicates)
  • 78 pr Silk Boxers
  • 702 pr High-cut briefs
  • 55 pr Low-cut briefs
  • 7 ea Banana warmers
  • 1 pr "Home of the Whopper" brief
  • 1 pr Vintage Joe Namath netted slingshot brief (prototype)

As MST3K never attained complete cultural devotion, Servo never appeared in many places outside of the show. During the promotional tour for Mystery Science Theater 3000: The Movie he and his pals appeared on shows such as CBS This Morning and MTV News to hype the film and riff on some stock footage from the news vaults. In the unsanctioned department Servo can be seen in the fan Star Wars-related series Troops in the episode "Stolen Robot" in which he is being smuggled as an illegal droid by some Jawas across Tatooine. An nonvisible mention of the red robot can also be found on a small sign on Star Trek: Deep Space Nine's promenade where there's an advertisement for "Tom Servo's Used Robots". Servo survived the crash of the Satellite of Love at the end of the series finale, Diabolik, and was last seen living with Mike Nelson, Crow T. Robot, and Cambot in a small apartment in Wisconsin where they continue to watch crummy movies on television, this time of their own free will.


References:
http://mst3kinfo.com/mstfaq/bots.html
The Mystery Science 3000 Amazing Colossal Episode Guide