Joel Hodgson, creator and host from the KTMA yearsthrough midway of Season 5, played Joel Robinson a janitor at Gizmonic Institute. He is shot into space by two mad scientists to run an experiments with cheesy movies. Joel creates 3 robots: Gypsy who pilots the Satellite of Love, Tom Servo and Crow T Robot who watches the movies with Joel and make wise cracks at the movies.

Micheal J Nelson took over for Hodgson midway through Season 5. Mike Nelson wass a temp worker that was shot up into space to take over the experiment when Joel escapes. Nelson was also a writer for the show. He made many cameos the most notable is Torgo.

 

Michael J Nelson's Webpage
Crow T Robot, the lovable wise-cracking robot, was played by Trace Beaulieu during the Comedy Central years and by Bill Corbett during the Sci-Fi years.
Tom Servo was played by Josh "J Elvis" Weinstein during the KTMA season and the 1st Season of the show. Kevin Murphy took over during the 2nd Season through the end of the series.
Gypsy pilots the ship and made a cameo appearance in the theater during Hercules and the Captive Women. Gypsy was played by Jim Mallon and was taken over by Patrick Brantseg late in the series run.

Trace Beaulieu played Dr. Clayton Forrester, a mad scientist, who shot a man into space and trying to torture him by making him watch bad movies. Beaulieu played Forrester from KTMA until the end of the Comedy Central run. He played Forrester in MST3K:TM.

He was also the voice of Crow T Robot during KTMA through the Comedy Central years.

Josh "J Elvis" Weinstein played Dr. Lawrence Erhardt for the KTMA year and through Season 1.

Weinstein's Stinkburger Inc.
After Weinstein left the show Frank Conniff, TV's Frank, took over as Forrester's right hand man. He played TV's Frank from Season 2 through Season 6 of the series

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