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3) "Two Days Before The Day After Tomorrow" | Season 9 | Watch Online  

A parody of the eco-disaster flick The Day After Tomorrow, this episode hammers the threat of global warming and its impending "attack" on the residents of South Park. Eventually, everyone finds themselves inside the crowded town community center, with news reports indicating that 600 billion people have died in Chicago alone. The situation continues to spiral out of control until everyone is informed that the environmental disasters outside were actually caused by crab people.

Best line: "We didn't listen!"

2) "Smug Alert" | Season 10 | Watch Online

The creators this time go after hybrids and the sterotype of their smug, environmentalist owners. In the beginning of the episode, only a few people drive hybrids in South Park — much to the dismay of others who can't stand their holier-than-thou attitudes. After one of the boys writes a catchy song that gets national play on the radio, however, everyone is soon driving in hybrids and acting like asses. In the end, the point is made that hybrids are good for the environment — but their owners don't have to be smug about it.

Best line: "The South Park and San Francisco smug is already at critical mass. If it gets hit by George Clooney's acceptance speech, it will be a disaster of epic proportions."

1) "ManBearPig" | Season 10 | Watch Online

Possibly the most quoted green-themed episode in South Park history, "ManBearPig" deals with Al Gore's quest to save the world from a creature that's half-man, half-bear and half-pig. The fact that nobody has ever seen such a thing doesn't deter Gore from warning everyone — even going so far as to dress up as the creature and scare children into believing it exists. The episode has received so much attention, that the real Al Gore has even been asked in interviews what his long-term strategy for dealing with ManBearPig is.

Best line: "ManBearPig doesn't care who you are or what you've done. ManBearPig simply wants to get you. I'm super serial."