Before Jim Harbaugh was the head coach of the San Francisco 49ers, he was a quarterback for the Colts and while he was quarterback for the Colts, he made a guest appearance on Saved by the Bell. Through the magic of the internet, we have the episode. Harbaugh appears at the 15 minute mark. (via CSNBayArea)
http://www.youtube.com/watch?feature=player_embedded&v=87d2duPjmjc