At 6:05, the first two doors on the right are both numbered 221. This error was not present when the doors were shown seconds earlier.
In this episode Butters' father's first name is Chris, while in later shows it changes to Steven.
This is not a goof, but rather an intentional change made to the character once his role became more prominent within the show.
This is not a goof, but rather an intentional change made to the character once his role became more prominent within the show.