Continuity mistake: When Eric comes running over to talk to the other 3 boys about the handicapped competition, their toy trucks are quite far apart from each other, but when it cuts from Cartman and then back to the boys, Kyle's truck has moved all the way in front of Stan's truck.
Continuity mistake: In the scene where Jimmy and Timmy are training, you can see that there are two people behind them, a girl wearing a pink top with a flower on and a boy with some green glasses on. When it cuts to Jimmy and Timmy talking, and then goes back, the boy wearing the glasses has disappeared, then a few shots later the boy with glasses is back.
Continuity mistake: When Cartman is planning out how he's going to be retarded, in the shot from behind him when he's on the computer there is a cup with a red and yellow pencil in it, the red is on the right and the yellow is on the left. Yet when it goes to looking at Cartman from the other way the crayons must've swapped positions because now they are the other way around.
Continuity mistake: When the handicapped people are on the bus, from a distance you can see that on the far window there is a kid nodding his head from back to front with black hair and when it goes into the bus you can see that the kid has brown hair and is nodding his head side-to-side.