Rincewind
I guess people think that Wizards are by definition old. Gandalf plays a big role in this ageist stereotype.
Ponder Stibbons is not yet a household name.
I'm still shocked that the same production used the same actor who played 2000+ year old Albert in Hogfather for rincewind.
Godsdammit! Rincewind is 30 tops in the first book.