John Denver died on October 12, 1997. He was killed when his experimental Rutan Long-EZ plane crashed.
Dr. Maphesto's character is the South Park representative of the North American Marlon Brando Look-a-likes. His character was originally inspired by Marlon Brando's character in The Island of Dr. Moreau (1996).
The music in the hallway scene is from a poem written by Jacques Prevert, "Page d'ecriture" or "Writing Sheet." It deals with the soul-crushing boredom of conventional schooling.