I'd have to go with Huey and Fenton just because one line puts it at the top.

SOME CANADIANS ARE FRENCH!

Seriously though if it wasn't for that line then I'd go with Dewey and Launchpad.

Really, just that?

Well I guess it's also because both Huey and Fenton are such loveable, comedically, dorky(not meant as an insult), nerds that just make me smile and laugh. Plus there are some things for both of them that I can really relate with.