Philip Glass appears in the background in the Season One episode, "Mr. Hankey, the Christmas Poo" as the minimalistic composer from New York who performs music during the "happy, non-offensive, non-denominational Christmas Play". He has not made another appearance on South Park. Stone and Parker strongly dislike Phillip Glass (not as much as Barbra Streisand though). They said can you basically "give a third grader a keyboard, tell him to mess around, sell that music as one of Phillip Glass' albums, and no one would know the diffrence."
Phillip Glass wears a black shirt, black pants, and has curly black hair. He can be seen in front of two gray keyboards.