Stan, Kyle, Cartman and Kenny do not appear in this episode. However, they are shown very briefly attending the school assembly at around 10:02.
In the scene where Dr. Janus first reveals his multiple personalities, one of the personalities says, "The horned toad says we should go to Mexico". The line is a quote from the movie The Outlaw Josey Wales, spoken by the character Lone Watie, portrayed by veteran actor Chief Dan George.
In the scene where Butters is playing as a trucker, he is quoting parts of the song "Convoy" by C. W. McCall.