I read a rumor of an unaired episode of the show some years ago. I did some checking back then and read the plot had something to do with both Steve and Carl going into his machine(forgot its name) and they both come out with switched faces. It was supposed to make use of 3d effects or something, but ended up getting canceled when it became too costly to produce. Anyway, I found a photo I got from a Family Matters newsgroup back then, that I found laying on an old HD I had stored away.
http://img251.imageshack.us/img251/9716/carlstevend9.jpg

I would have loved if this episode actually got somewhere as it looks hilarious! It makes you wonder how far production got as this scene was actually filmed and digitally edited? If any experts can help that'd be great! :D