In season 4 Episode 1 " Cartmans silly hate crime" the girls challenge the boys to a sledging race. The girl who challenges them says that the race will be on SATURDAY and Kyle confirms the race being on saturday. Near the end of the episode when kyle, Stan and Tolken go to the Governour to try and get cartman released from prison, Kyle says that they need him to win the sledging race on THURSDAY not Saturday.