funny you should mention chevy chase... he's the actor who did a lot of prat falls and such while doing his gerald ford impression on saturday night live (which is why i think of gerald, who was president before i was old enough to be aware of presidents, as a clumsy guy). probably also why yvonne is thinking of him as falling down a lot.
leslie nielson also does a lot of pratfalls, but i get the feeling you're looking for someone who is actually clumsy, not someone who fakes it.
dan quayle was known for saying a lot of very strange/stupid/silly things, but he wasn't really known for falling down a lot.
can't think of too many other people, really.
there's inspector cluseau (sp?) from the pink panther, but i'm not sure if he'd work for you.
there's clark kent from the chris reeve movies, but somehow i doubt you want to use him.
leslie nielson played lt frank drevin on the tv show "police squad" (which later became the "naked gun" movies), but i'm not sure how well the character would be recognized.
sorry i can't be of more help. chevy chase's gerald ford is the best i can think of.
oh.. one more -- homer simpson. again, not a real person, but he is known for impressive levels of clumsiness, stupidity, and general ineptitude.
Paul, doing a quick fly-by while on vacation, and trying to make do with 28.8.
