That’s just wrong. Frogs are very smart at being frogs.
This post is mostly just an excuse to share New Frogs!
Doesn’t have two brain cells to rub together.
Doesn’t have the brains that God gave geese.
Dumber than a ditch carp.
As sharp as a napkin.
As thick as two short planks.
“Dumber than a Straight Dope contributor’”
Dumber than a bucket of butt-holes.
Or a BOB for short.
Dumb as shit.
Doesn’t have the sense God gave a lemon.
My fave has always been “a bag of wet hair”.
Others, but not mine:
Doesn’t have the sense God gave paste.
Couldn’t pour piss out of a boot with instructions printed on the heel.
and, for the Southerners, “Bless His Heart”.
I’ve always liked to introduce myself to the rest of the dart teams as the Goalie for my team. (I don’t usually shoot and most of the time I am the alternate.)
My own (*very *idiosyncratic) one: “Dumber than a mime with laryngitis” (OK, people… think about this for a second… :))
“Room Temp. IQ,” which has been mentioned, is good, too. Unless you’re using a proper temperature scale… 
I’m partial to “had a dumbass attack” or “had a case of dipshit syndrome.”
“Dumber’n a” doesn’t see a lot of use out here. We have a more sophisticated class of insults: “Not the brightest bulb”, “not the sharpest tool in the shed”, etc.
Comically, some of our less sophisticated insulters mix these up and end up calling you “not the sharpest bulb in the drawer”. And that’s just dumber’n a box o’ lights iffn ya ask me.
In related news, this whole kerfuffle reminds me of a great quote about someone trying to figure a machine out:
“He just kept turning it over like a monkey trying to fuck a football.”*
- Our friends from the Eastern hemisphere should picture an American football or a rugby ball, not a freakin’ Teamgeist.
I also like a quote my friend had up on MySpace for a while: “When God was handing out brains, you thought he said ‘gay sex’.”
After this thread, I’m going to start saying people are “dumber’n a goalie in darts”.
Hostile Dialect,
Hostile Dialect, Narcissist
I’m partial to bag of hammers,
but pn the dope I picked up ‘not the swiftest wildebeast on the serengeti.’ love that
Dude’s dumb to the left of the navel and dumb to the right of the navel. Less polite body parts can be used in other fora, but this is IMHO.
Doesn’t have the sense God gave to a pebble.
His mom dropped him on his head.
His mom dropped him on his head, but it’s not like he’d been using it before that.
A burnt-out lightbulb shines brighter.
An IQ below room temperature outdoors in the South Pole thereabouts of July 25th at midnight, and I don’t mean Kelvin.
His IQ is so low it’s gone beyond floor level, all the way through the Earth and out the other side.
This one’s from my brother: Normal folk have Intelligence Quotients, he’s got an Intelligence Deficient. (It’s more alliterative in Spanish: La gente normal tiene coeficientes de inteligencia, lo suyo es un deficiente de inteligencia.)
Dense as a fruitcake.
Strong like bull; smart like dumptruck.
Sharp as a marble.
You must be thinking of, “Ugly as a hat full of assholes.”
I usually use these:
Dumb as a sack of hammers.
Dumber than a box of rocks.
Short and to the point:
Dumb as a stump.
I hear these a bit - but I am surprised to be the first poster (I think) to offer up “dumb as dirt” - I hear that all the time…
Dumb as a door nail.
Although I think I have picked some new ones up in this thread.