Takes him an hour and a half to watch “60 Minutes.”
Couldn’t find their backside with both hands.
Here is an older one and refers to Princess Diana who left school with no academic results.
He has as many O-levels as Princess Di
This person is a hewer of wood and drawer of water, or more succinctly, he is a hewer and drawer.
has all the brains god gave a #2 pencil
If brains were dynamite he wouldn’t have enough to blow his nose.
If brains were rubber he wouldn’t have enough to make a flip flop for a one legged budgie
A few croutons short of a salad (this is my current favorite, since it was recently used to describe someone name Caesar).
One that was a favorite from my middle school days:
If brains were gasoline, you wouldn’t have enough to power an ant’s motorcycle around the inside of a Cheerio.
…and a flashlight.
Dim bulb
A few elements short of a periodic table.
…and a six-man search team.
He’s Tory. (or Labour, or Whig, or whatever political party you disparage)
Couldn’t spell “cat” if you spotted him the “c” and the “t” and let him buy a vowel.
His cheese slipped off his cracker.
As dumb as a bag of hammers
Not the brightest lighthouse on the coastline
A few sub-units of currency short of a standard unit. I’ve heard “A few shillings short of a pound,” “a few centimes short of a franc” and “A few kopeks short of a ruble.”
As dumb as a box of hair.
I’ve always liked “A few clowns short of a circus.”
his expression is like a goldfish with a concussion…
He’s half a bubble off plumb.
Nothing between the earmuffs.
The gate is down, the lights are flashing, but the train ain’t coming.
He’s a couple teats short of an udder.
A brain like a dehydrated bb (thanks to Captain Lou Albano).
Fucked up like a soup sandwich.
Fucked up like a football bat.
He thinks the Mexican border pays rent.