The Robinsons' water crisis deepens when Dr. Smith uses their only water supply for a shower. But a strange alien fruit may be the answer-until it causes Smith to grow to twice his normal size.
An oddball family of alien hillbillies ensnares the Robinsons. Their daughter tries to romance Don while their pet werewolf and fast-growing, man-eating plants spell trouble.
Glowing humanoids invade the Robinsons' colony in search of a brain to navigate their ship. Their plan is foiled when Will's worry over his parents' safety makes his brain unusable.
Chaos reigns as the Keeper's creatures, let loose by the robot and Dr. Smith, overrun the planet. The Keeper refuses to stop the heinous animals unless the family gives him Penny and Will.
The Robinsons try to persuade a long-stranded astronaut, James Hapgood, to take Will and Penny back to Earth. He refuses, but has a change of heart after a near tragedy befalls Penny.
The Robinsons set up camp on a planet populated by strangely evolving life forms. As the family moves their camp in search of warmth, they are confronted by a giant Cyclops.
The family comes upon an evil alien zookeeper, whose trance-like powers can entice exotic animals-and young humans like Will and Penny-to follow him into captivity.
Following a tense effort to rescue John Robinson from deep space, the Jupiter 2 is drawn inside a massive alien spaceship. There, the family confronts a strange race of bubble creatures.