South Park: Bigger, Longer & Uncut 1999

The third graders of South Park sneak into an R-rated film by ultra-vulgar Canadian television personalities Terrance and Phillip, and emerge with expanded vocabularies that leave their parents and teachers scandalized. When outraged Americans try to censor the film, the controversy spirals into a call to wage war on Canada and Terrance and Phillip end up on death row, with the kids their only hope of rescue.