Corrected entry: Usually Butters' house has a green interior, during this episode, it has a dark blue interior.
Corrected entry: When the boys are at the amusement park with all their potential new friends, Ike is with them, not only is Ike Kyle's little brother who is in kindergarten, not 4th Grade like all the other kids, but Kyle is always trying to get rid of Ike. Why would Ike be in competition to be one of the friends?
Correction: Since Ike is always following Kyle around, he obviously wants to be one of the boys. Kyle probably let Ike enter the contest just to get his entry fee, with no real intention of letting Ike make the final 10.
Correction: This is not an error. A green interior switching to a blue interior within the same episode or scene would be an error. Good Trivia? Yes. Mistake? No.