South Park: Season 2, Episode 11

2 - 11: Roger Ebert Should Lay Off the Fatty Foods

The boys go on a class trip to the planetarium. Afterward, they all want to go back, though they can't remember why. Stan, Kyle, and Kenny investigate and realize that the planetarium has been brainwashing people. Meanwhile Cartman tries his best to get in a Cheesy Poof commercial.