In Create-A-Superstar, go to "Profile", and go to the screen where you give them their name, call, voice, etc. Go to the the sign selection screen. Search around the bottom and top of each page, and you will see signs reading "What's this All Aboot?", which was a line said in "South Park: Bigger, Longer, and Uncut", and a sign reading "Blame Canada", which was a song used in the same movie.