Hey dol! Merry dol! Get lost Tom!!!

[dancing spawn of ungoliant]

Originally Posted by Boromir88

Even most BOOK readers have trouble figuring out who/what Tom Bombadil is.

Exactly!

I had terrible difficulties in picturing the elves in my mind when I first read LotR. After I saw the Fellowship, I adapted my frail image of the elves to correspond the movie version. I have same kind of difficulties with Tom. It would be easy if someone just showed me a picture: "Look, here's Tom, he looks like that." But since Tom is such a mysterious character, maybe it's appropriate to have a little blurred mental picture of him. Seeing him on the film would probably have been a disappointment.
Like The Saucepan Man said

The difficulty would be in finding an actor who could portray the right mix of levity and underlying power.