It's easy to write a dumb character: It's essentially like writing a normal character, only you don't have to bother with a personality or any semblance of intelligence. A good dumb character, however, is damn near impossible. Why? Because it's hard to make a blank slate likable. But when you do, it's pure fucking comedy GOLD. For the sake of qualifications and so that you guys don't end up sending me the obligatory "YOU FORGOT THIS PERSON GRAAAAAAAH!" comments, in order to make the list, the character must be on TV, must be purposefully written dumb, and have to be both funny and at least likable on a personal level. Also, I eliminated any character that was on a show comprised entirely of stupid people (i.e. The Simpsons, Family Guy, South Park, etc.) And now, in absolutely no particular order whatsoever...
Hank Yarbo (Corner Gas)
Sample Dumb: "(Re: The riddle about where you bury survivors) OHHHHH! The *survivors* ... Bury one on each side.
T (United States of Tara)
Sample Dumb: I'm here because she went all CSI on your pubic patch you call a backpack and found those kill pills I got you.
Sample Dumb: Did you know that dolphins are just gay sharks?
Philip J. Fry (Futurama)
Sample Dumb: He wasn't an astronaut, he was a sitcom actor. And he was only using space travel as a metaphor for beating his wife.
Cerie Xerox (30 Rock)
Sample Dumb: These sunglasses have a chip in them that makes the lenses change color as my iPod loses power!
Anya Jenkins (Buffy The Vampire Slayer)
Sample Dumb: I like you. You're funny and you're nicely shaped, and frankly it's ludicrous to have these interlocking bodies and not... interlock. Please remove your clothing now.
Valerie Cherish (The Comeback)
Sample Dumb: You see puppies, I see Korean barbeque!
Buster Bluth (Arrested Development)
Sample Dumb: No mother, I can blow myself. You've interfered for the last time.
Michael Scott (The Office)
Sample Dumb: I guess the atmosphere that I've tried to create here is that I'm a friend first and a boss second, and probably an entertainer third.
Meatwad (Aqua Teen Hunger Force)
Sample Dumb: I don't have any real dolls, I prefer to use my infinite imagination... cause I ain't got no damn money.