Updated: March 08, 2008

By Bruce Fedow:

Monsters and aliens played a co-starring role in most episodes of Lost in Space. From the second episode "The Derelict" where the Robinsons come face to (slimy) face with "a shipload of non-human colonists" in John's own words to the final episode "Junkyard of Space" featuring the intergalactic junkman, these denizens of space sometimes helped the Robinsons or be friended Will and Penny but the majority of them spelled trouble for our galactic castaways.

Perhaps the most famous of these creatures was the one-eyed Cyclops, first seen in the episode "There Were Giants in the Earth" but so popular it was re-used in "The Keeper" and "Flight Into the Future."

Another monster was basically a bear costume, complete with claws, that Irwin Allen and his assistant Paul Zastupnevich cleverly recycled for many episodes. Actor Charles Dierkop glued some fur to his face and first donned the suit in the episode "One of Our Dogs is Missing" and a shaggy head with horns and light-up eyes transformed the costume into a new monster for "The Keeper's" menagerie. Remove the horns and eyes and you've got Officer Bolix' space watchdogs in "All That Glitters." Add a single ugly eyestalk and the Hairy Beast from "Magic Mirror" is born!

A large windup key in his back and you've got "The Toymaker's" furry enforcer. A pirate outfit and the beast was ready to search for the "Treasure of the Lost Planet." Of course there were aliens as well as monsters. The bubbleheaded aliens in the unaired pilot became the "Invaders From the Fifth Dimension." In later episodes the same headpiece changed Vincent Beck into Megazor in the "Hunter's Moon" episode and created a family of aliens who enjoyed their "Day at the Zoo."

One of the more interesting alien life forms were the Saticons, a trio of troublemakers with glittering faces, hands, derbies and a burning desire to rule the universe! They were used in two episodes, "Wreck of the Robot" and "The Galaxy Gift."

Several creatures, while interesting to look at, were merely masks with immobile mouths like Mr. Keema and the Frog Alien in "The Golden Man" and Lemnoc in "The Phantom Family." Allen's penchant for reusing most monsters extended to his three other series as well. A purple Lemnoc reappeared in the Time Tunnel episode "Town of Terror." The alien amphibian in "A Change of Space" popped up in Voyage to the Bottom of the Sea episodes like "The Mermaid" and "The Menfish." And even the Cyclops-minus his shaggy skin-was in the Land of the Giants episode "Double Cross."

So if you're watching an episode of Lost in Space and you think you've seen that monster or alien somewhere before-you probably have!