"Canon in D" is a composition by Johann Pachelbel. It was heard in the Season One episode, "Cartman's Mom is a Dirty Slut" as the background music for Eric Cartman's tea party with his dolls.
When Cartman fails to come to school, Stan Marsh, Kyle Broflovski, and Kenny McCormick go to his house to investigate.
Mr. Mackey, the school counselor, sends them back with his video camera in order to study his odd behavior. The other boys watch and video tape him secretly playing tea party with his dolls; Clyde Frog, Rumpertumskin, Polly Prissypants, and Peter Panda.