The Mole People are named after Gerry and Sylvia Anderson, the creators of the Thunderbirds series, who made the first two films that the Mystery Science Theater 3000 crew riffed on in the KTMA days -- Invaders from the Deep and Revenge of the Mysterons from Mars.
The Mole People disappeared after Season 3. According to the MST3K FAQ:
|“||The Mole People costumes were horribly hot under the studio lights, and the people (usually unpaid interns) who were inside of them rebelled and refused to continue the characters, for fear of asphyxiation. ||”|