Lost in Space

S03E19 The Promised Planet

The Robot unexpectedly informs the crew that the Jupiter II is nearing Alpha Centauri, leaving everyone astonished. Upon landing on a mysterious planet, they encounter a group of seemingly teenage Earthlings. However, these individuals are actually aliens who live in a hippie-like society and cannot age. Desiring to experience normal aging, they devise a plan to have the older members of the Robinson family depart in the Jupiter II while the younger ones remain for an experiment. The aliens manage to persuade the older members to leave, but Will cleverly outsmarts them. Ultimately, the Jupiter II returns to rescue Penny, Will, and a disguised Dr. Smith, who has deceived everyone into believing he is young.