Well, for the record, Peter Griffin was formally diagnosed as being mentally retarded (just), so by my books, his I.Q. would be 69, tops.
…Though I just did a little checking, and it seems that Homer Simpson’s normal IQ was established as being 55. Although it must be noted that he has a long history of severe brain injuries—that, combined with some of his other behavior, makes me wonder if he actually has some form of induced Autism.
Oh! I got one…“Billy,” from The Grim Adventures of Billy and Mandy. (Who, if he were found to be suffering from some kind of organic brain disorder, wouldn’t suprise me too much.)
Beavis and Butt-Head.
I’m surprised no one has yet mentioned Ralph Wiggum. He’s so dumb he can’t even do most of the dumb things these other characters do.
I can’t believe I didn’t think of that. They’re both incredibly stupid, though in the movie they have some great luck.
Actually, I believe it was established in one episode he has a crayon stuck in his brain that has a lot to do with his low intelligence. When it was removed once, he become rather smart.
And Even so, Homer can be occasionally be intelligent.
Chinese Adoption Agent: “Only you can save our communist dictatorship!”
Homer: “Communist? Then why am I seeing rudimentry free markets?”
Lisa: “Dad! You’re driving on a Roman Aquaduct!”
Homer: “What am I susposed to use it for? Transporting water to urban centers?”
Earlier in the same episode he also said something rather intelligent about Italy.
Between Homer and Peter, I’d say Peter is dumber.
Well, to be fair, if Meg was my kid, I’d probably do the same.
Yes, I love it when they beat up on meg. She’s so fricken annoying that I can’t feel sorry for her except on rare occasions.
Actually, I think that’s more “being a guy” because it seems it took him almost that long to realize she was interested. Happens to a lot of guys.
Anyone who is both a promising Doctor and manages to get in and out of a non-existant alliance research lab with isane sister in tow doesn’t belong on “stupidest list”. Hell, the whole infiltration thing would probably earn him a career in episnoge if he wanted one.
There seemed to be a lot of dim bulbs on “Green Acres.” Mr. Kimball (sic?) comes to mind.
Speaking of King of the Hill, Hank’s niece, Luanne (???) would get some pretty low scores.
Although Ignatowski had some very non-intellectual moments, he seemed to have a very high emotional intelligence, really was the literal “heart” of many episodes. Best. Sitcom. Character. Ever. IMHO.
Fry and Amy are battling it out for second. The dumbest character on Futurama has to be the clueless Zap Brannigan.
You know, that’s an interesting choice. In a way, Oliver Wendall Douglas himself was pretty dumb. Ostensibly, he was a smart lawyer and all that, but he could never quite figure out that he was like Alice in Wonderland. He never learned how to interact with his environment.
I agree, hey wait a minute wasn’t Ignatowski Moonchild spelled backwards? 
Major the Dr. Frank Burns, of MAS*H.
His bumbling & incompetence, compounded by snobbishness & paranoia, fill the graveyard.
“Me fail English? that’s unpossible!”
Dude, you’re missing the point. He failed to make his moves on KAYLEE! She’s cute. She’s smart. She’s sweet. She’s hot. Simon Tam was an idiot!
All those guys who failed to move on Bailey and Mary Ann were likewise morons.
Simon wasn’t so much dumb as he was too overly civilized to just make his move, and prone to putting his foot in his mouth when he did try to gently woo her. Also, he kinda resents having to be exiled to the ass end of the 'Verse. His work on Ariel alone disqualifies him for this list.
Besides, he got his shit together in time for the movie.
The entire cast of Will and Grace.
I’m surprised no one has mentioned Jim and his brother-in-law on According to Jim.
DISCLAIMER: I do not regularly watch this show but I have caught several episodes on occasion. Every episode is the same, Jim tries to hide something/put something over on his wife (who’s way out of his league), he comes up with some elaborate lie/scheme, brother-in-law goes along with it and wife always finds out gets mad then forgives him. The guy never learns a lesson.
Alice Horton on The Vicar of Dibley
Most of the jokes Dawn French tells after the credits (she tells them to Alice) are a shining example of her dimness.
While Coach was definitively clueless, Woody remains a bit more of an enigma. When it came time for a raise, Woody tricked Sam into giving him a larger raise than intended. Also remember that Woody was involved in theater and wanted to be an actor.
My opinion is that Woody’s “dumb rude” shtick was designed as a conversational method to disarm people- note that he never ended up in trouble for doing something stupid (as opposed to many of the other people listed here), but rather just had jokes made about him. (Or acted as the unwitting punchline to his own jokes.)