The background sound used in the future after Cartman breaks up Mrs. Garrison and Richard Dawkins is the background ambience from the holographics room on seaQuest DSV.
The sea otters, like the apes are animals who have evolved to the level of speach in the future and are at war with humans. They ride ostriches like the apes ride horses, sound similar battle horns before fighting and one shot of them running accross a corn field is based on a scene from this film.