- For the student who first appears in Season 3, see Sunshine.
Hippies are the test subjects of Leonard 20 years before the events of "Prom Face/Off". His experiment was intended to reverse the alleged devolution that occurs in hippies. If left alone, they revert to chimpanzee behavior. When Leonard's experiment failed, he burned down the building the experiment was held in, which supposedly killed them all off. But, 10 hippies remained alive, one of whom being Leonard's lover from that point to the present.
In the present, during "Prom Face/Off", the Dean holds a school dance in the burned building, which he renovated. Baby Cakes finds one of the hippies, Mattie, and falls in love with her, unaware that more are lurking inside. As the dance is being held, Baby Cakes, at his home, shows Mattie to Leonard. A now-frightened Leonard becomes even more scared when told about the dance, and he makes his way to it. There, the other hippies manifest themselves, attacking the people at the dance. Leonard calls them to attention, and he explains his experiment and that he too fell in love with one of the hippies, Haystack.
When Leonard and Haystack are crowned Prom King and Queen, they're given a new car as a prize. Leonard gives it to the hippies, allowing them a fresh start, but they instead drive into a building, causing an explosion and leaving their fate unknown.
In addition to Mattie and Haystack, the other eight hippies' names are Sunshine, Moonbeam, Fungus, Weave, Streamer, Mud Pile, Husk and Lice Bed.