Magic Voice - a disembodied female voice that would warn the crew of upcoming commercial breaks and make other announcements.
Jerry and Sylvia - two "mole people" from the movie The Mole People who occasionally assisted the Mads and stopped by for social events. They also work Deep 13's camera in the first host segment of "Lost Continent". Presumably named after Sylvia and Gerry Anderson, the creative team behind ' and Supermarionation shows like Thunderbirds and Stingray, some of which were featured as KTMA-season episodes.
Jack Perkins - in real life the host of the A&E Network's Biography program, Perkins first appeared in MST3K simply to annoy the Mads by describing the movie with glowing praise. When MST3K appeared in syndication as The Mystery Science Hour, Nelson's fake "Jack Perkins" hosted the show.
Torgo - a monster/henchman in ', Torgo was among the most frequently returning "guest characters" of MST3K. He got his knees fixed and returned as "Torgo the White" to accompany TV's Frank to "Second Banana Heaven" and was never seen again.
Jan-in-the-Pan - a woman's severed head from the movie The Brain That Wouldn't Die.
Santa Claus - appeared three times on the show, including a fight with Pitch, bellowing, "I'm here to chew candy canes and kick ass, and I'm all out of candy canes!". Portrayed twice by Kevin Murphy and once by Joel Hodgson.
The Nanites - self-replicating, bio-engineered organisms that work on the ship, they are microscopic creatures that reside in the S.O.L.'s computer systems. The Nanites made their first appearancein season 8. Based on the concept of nanotechnology, their comical deus ex machina activities included such diverse tasks as instant repair and construction, hairstyling, performing a Nanite variation of a flea circus, conducting a microscopic war, and even destroying the Observers' planet after a dangerously vague request from Mike to "take care of little problem". They also ran a microbrewery. The Nanites were largely forgotten about during the show's last season, and we are not given an explanation of their fate following the series finale.
*Kevin Murphy played Wade the Nanite.
*Paul Chaplin played Ned the Nanite.
*Mary Jo Pehl played Jody the Nanite and Shelli the Nanite.
"Krankor", who appeared in a host segment during the "Prince of Space" episode, and returned three episodes later in a host segment for "Invasion of the Neptune Men", featuring a movie with a similar plot. He was a vain, would-be conqueror with an unfortunately chicken-like appearance and a drawn-out, braying laugh.
