Use these at your own peril.
He's a couple of knights short of a Crusade.
He's a couplet short of a sonnet.
He's a few ears short of a bushel.
He's a few feet short of the runway.
He's a few links shy of a chain.
He's a few puppies short of a pet shop.
He's a few tomatoes short of a thick sauce.
He's got a room temperature IQ.
He's so fat, when he dances the band skips. (thanks to Tim Lister)
He's about a half a bubble off plumb.
He's all lime and salt, but no tequila.
He's an experiment in Artificial Stupidity.
She's so fat, when she walked in front of the television, the kids missed 3 commercials. (thanks to Tim Lister)
His antenna doesn't pick up all the channels.
He was born during low tide in the gene pool.
He has both oars in the water, but they're on the same side of the boat!
He can't find his ass with two hands and a periscope.
She's deaf, dumb, and blonde.
His deck has no face cards.
He is diagonally parked in a parallel universe.
He doesn't have his belt through all the loops.
She's eating with only one chopstick.
Her elevator doesn't make it to the penthouse.
God might still use him for miracle practice.
His jogging trail doesn't go all the way around the lake.
He left the store without all of his groceries.
He's missing a few buttons on his remote control.
No grain in her silo.
He's not the quickest bunny in the forest.
She's one song short of a musical.
She's so ugly it looks like her face caught on fire and she tried to put it out with a screwdriver. (thanks to Joel)
Her slinky is kinked.
Some M and Ms are missing from her bowl.
He's strong like bull, smart like streetcar.