Many Ways to Say "Stupid"

NOTE: At the end of this is an absolutely true story that goes along with all of these sayings.

Comparative:
Bright as Alaska in December
Not the sharpest knife in the drawer
So dense that light bends around him

Objective:
Has a room temperature IQ
Takes him 1-1/2 hours to watch “60 Minutes.”
Fell out of the family tree
Was left on the Tilt-a-Whirl a bit too long as a baby
One-celled organisms out-score him in IQ tests
Donated his body to science before he was done using it
He has two brains...one lost and the other loose

Speculative:
If you stand close enough to him, you can hear the ocean
If you give him a penny for his thoughts, you’d get change back
Probably got into the gene pool while the lifeguard wasn’t watching
If brains were taxed, he’d get a rebate
Some drink from the fountain of knowledge, he probably gargled

Metaphoric:
Gates are down, lights are flashing, but the train isn’t coming
Elevator does not go to the top
Wheel is turning, but the hamster is dead
Lights are on but nobody is home
Full 6-pack, but nothing holding them together
Doesn’t have both oars in the water
Train of thought is still boarding at the station
A sandwich short of a picnic
A brick shy of a load
Not firing on all thrusters (or, pistons)

OK, this is a true story:
When I was working in another department at a local university, we had this guy who was in charge of taking care of all of our computers. He was ... well, let’s just say that he seemed to lack any social skills (and was probably so dense that light bent around him because he didn’t keep the job for very long). One day this guy was working on some computers in faculty offices, and I was in the main office joking with one of the graduate assistants about how dense this guy was. Pretty soon, she and I were trading little quips like, “A sandwich shy of a picnic” and “Elevator doesn’t go to the top floor.” After a while, this guy came back into the main office. He needed 50 cents to get a can of pop from the vending machine, but he didn't have enough money.

Honest-to-God, this guy asks us, “Have you got any change? I’m a dime short of a pop.”