She has cobwebs in the windmills of her mind.

She's so stupid she thought Taco Bell was a phone company in Mexico.

She's stupid she was fired from M&Ms for throwing away the "W"s.

She's so stupid she cooks with Old Spice.

She's so stupid she tried to strangle herself with a cordless phone.

She's so stupid she took the Pepsi Challenge and chose JIF.

She climbed into the gene pool when the lifeguard wasn't looking.

She fell out of the family tree.

She's a can short of a six pack.

It doesn't appear that her elevator stops on all floors.

She's one of the dimmer bulbs in the pack.

If dumb were dirt, she'd have about 40 acres...

That gal is dumb enough for twins...

A taco short of a combination plate...

Dumber than a box o' rocks...

"She's as sharp as a sack of wet mice."

"She's not the sharpest spoon in the drawer"

"She's a few bits short of a byte."

Her elevator doesn't go all the way to the top.

"She's so stupid she couldn't pour piss out of a boot with directions on the heel.

She came from the short end of the gene pool"

If she were any more stupid, she'd have to be watered twice a week.

If you give her a penny for his thoughts, you'd get change.

If brains were taxed, she'd get a rebate.

She would be out of his depth in a parking lot puddle.

She has serious delusions of adequacy.

She sets low personal standards and then consistently fails to achieve them.

She's depriving a village somewhere of an idiot.

She's a gross ignoramus - 144 times worse than an ordinary ignoramus.

The gates are down, the lights are flashing, but the train isn't coming.

She's so dense, light bends around her.

She suffers from Clue Deficit Disorder.

During evolution her ancestors were in the control group.

An intellect rivaled only by garden tools.

Some drink from the fountain of knowledge, but she just gargled.

She has a mind like a steel trap - anything entering gets crushed and mangled.

She is so stupid that people around her are at risk of second hand idiocy.

She couldn't find her way through a maze even if the rats helped her.

She doesn't just know nothing; doesn't even suspect much.

Mind readers charge her half price.

She ought to have a warning label on her forehead.

She's a waste of genetic material, better suited for a head of lettuce.

She's so stupid, she fell out of the stupid tree, and hit every branch on the way down, got up, tripped over the ugly stick, and decided to try the tree again.

She's so stupid she thinks the Mexican Border pays rent.

She is not the brightest coin in the fountain.

She's so stupid, she went up to a parking meter, put a coin in and expected bubble gum to come out.

She's so stupid, she got hit by a parked car.

She's two bricks short of an analogy.

She's not just stupid. It would take a million years for the light from stupid to reach her!

She was absent the day God handed out brains.

The lights are on but nobody's home.

Several cards short of a full deck.

She is as sharp as a marble.

To call her stupid would be an insult to stupid people!

I've known sheep who could outwit her.

She's the Village Idiot of the Disenchanted Kingdom.

Easily confused by shiny objects.

She doesn't use birth control 'cause the pills keep falling out.

Someone needs to put more chlorine in the gene pool...

She's so stupid, she consistently loses a battle of wits with bricks.

Sniffing glue made her smarter.

She'd get lost falling down.