Martin Van Buren, the eighth President of the United States (1837-1841), has appeared in a bust, on some coins, and on a post-it note. It isn't known if The Cheat and Strong Bad have anything against him or if they idolize him or something. He might appear more.

He has been in:
The Cheat's Character Tape
StrongBadEmail/2 emails
Three Times Halloween Funjob