South Park S04 E11 Fourth Grade

"Four boys. One f**ked-up town."

The kids have to face the 4th grade, and they're not too happy about it. Cartman cooks up a scheme to go back in time to return to the 3rd grade where things were fun and easy. Two geeks help them rig Timmy's wheelchair into a working time machine and send Timmy on the trip of his life!