The Zoo: San Diego (2019)

S2E11 Roger Ebert Should Lay Off the Fatty Foods

The class takes a trip to the planetarium, but while everyone else seems off, Cartman is in his usual form. Stan and Kyle, along with Kenny’s ultimate sacrifice, set out to uncover what's making their friends act so strangely. Meanwhile, Cartman finds himself landing a spot in a snack commercial. As the four friends dig deeper, they begin to unravel the bizarre happenings at the planetarium.