Al Gore's obsession with ManBearPig is supposed to be a spoof on Gore's high profile activism regarding climate change, as Parker and Stone did not believe in it at the time of the episode. The episode "Time to Get Cereal" from 2018 can be seen as a sort-of apology to Gore as the topic is taken much more seriously, as Parker and Stone have since changed their opinion on the issue.
The creature, ManBearPig, may have been inspired by the 1983 film, "Extraterrestrial Visitors", later re-named Pod People. The film is about an alien monster that lands on Earth and attacks some poachers and teenagers. When the poachers confront the monster, one remarks, "Looks like a cross between a pig and a bear." The obscure film became more recognized when it was riffed in a 1991 episode of Mystery Science Theater 3000.
In the disappearance of Dennis Martin (1969), there have been witnesses who claimed to have seen some man-bear-pig-like creature, abducting the child. The creators might have gotten some inspiration from this story.
The bottle that Cartman holds as he eats treasure is spelled wottur
The synthesized score and POV shots used as Al Gore, dressed as ManBearPig, approaches the boys in the park are heavily influenced by the werewolf attack scenes in Silver Bullet (1985).