I believe that "One Got Fat" is definitely real. I saw it on another website and a few comments came from people that remembered seeing it as kids. Besides, that is most definitely Edward Everett Horton or the most talented impersonator in the world.
The "Bike Camp" video is awful. I couldn't make it three minutes into the first part. The song is not only awful, that style of rap was already old school in 1989. I've got to hand it to the guy in the pink shirt, he was a good actor to get through that crap without a whipped dog expression on his face. I guess that was his best paying gig he had ever gotten.