Sea People, a none to subtle parody of Sea Monkeys, appeared in the South Park episode titled "The Simpsons Already Did It" from the shows 6th Season.
UPDATE: You can now watch the full episode of South Park featuring Sea-Monkeys for free online at www.SouthParkStudios.com. Click here to go straight to this episode.Click Images to Enlarge
Cartman excitedly buys the Sea People "Buried Treasure" kit.
He dreams of growing a new world of little Sea People so that he'll no longer have to deal with the real world, the one that's "full of hippies."
Cartman is enraged to discover that the sea people aren't actually little people.
Through a typically disgusting (and hillarious) set of circumstances he does eventually end up with actual little Sea People, and they worship him (except for the other sect, who worship Tweek.)
Read the wikipedia entry for this episode here.