These are actual lines out of OER (Officer Efficiency Report) performance appraisal for the military.

• Not the sharpest knife in the drawer.
• Got into the gene pool while the lifeguard wasn't watching.
• A room temperature IQ.
• Got a full 6-pack, but lacks the plastic thingy to hold it all together.
• A gross ignoramus - 144 times worse than an ordinary ignoramus.
• A photographic memory but with the lens cover glued on.
• A prime candidate for natural deselection.
• Bright as Alaska in December.
• One-celled organisms out score him in IQ tests.
• Donated his body to science before he was done using it.
• Fell out of the family tree.
• Gates are down, the lights are flashing but the train isn't coming.
• Has two brains; one is lost and the other is out looking for it.
• He is so dense, light bends around him.
• If brains were taxed, he'd get a rebate.
• If he were any more stupid, he'd have to be watered twice a week.
• If you give him a penny for his thoughts, you'd get change.
• If you stand close enough to him you can hear the ocean.
• One neuron short of a synapse.
• Some drink from the fountain of knowledge...he only gargled.
• Takes him 1.5 hours to watch 60 minutes.
• Was left on the Tilt-A-Whirl a bit too long as a baby.
• Wheel is turning, but the hamster is dead.