I popped in the Cars DVD just now, watched "Mater and the Ghostlight" (fun little short cartoon, would've been perfect for Halloween, a week too late now, oh well), and then I watched the deleted scenes.
In one clip, after McQueen arrives in town, the townsfolk want him to race in the first ever Radiator Springs Grand Prix. He refuses, opting for "standard community service". Later, he wakes up and finds out what that entails: Doc Hudson removes his engine and puts it into a steamroller, transferring McQueen's mind and personality into the steamroller and leaving his body an empty shell. Basically the car equivalent of a brain transplant! He tries to escape, but isn't used to the fact that he can't go very fast now. They set him to work repaving the road he tore up.
Meanwhile, just for fun, Mater gets Doc to put his engine into McQueen's body. As Steamroller McQueen works at repaving the road, Lightning Mater has fun being a racecar (a bucktoothed one), zipping around all over the place. "You're all MONSTERS!" says McQueen. "DON'T YOU WRECK MY BODY!" Then Mack shows up to take McQueen to L.A., but fails to recognize him and thinks Mater is McQueen! Mater gets into the trailer and heads off to L.A. with McQueen's body.
But then he wakes up again and he's back to normal. It was just a dream!