Most stories have a kooky character in them. Usually it isn't the main character, but a pretty significant secondary character. When I say "kooky", I don't necessarily mean "funny."
In Neil Gaiman's The Graveyard Book, Silas plays this part. He's mysterious, yet all-knowing. It seems as if he watches over Bod as his duty, yet he generally cares about Bod. He's odd in that he's not the typical ghost who lives in the cemetery - he can leave, where the other ghosts are stuck inside the gates.
Bod is only one example of a kooky character. Can you think of more?