If you have the personalities down, you understand them and identify with them; you can stick them in any situation and have a pretty good idea of how they're going to respond. Then it's just a matter of sanding and polishing up the jokes. But if you've got more ambiguous characters or stock stereotypes, the plastic comes through and they don't work as well. These two characters clicked for me almost immediately and I feel very comfortable working with them.

Bill Watterson