"A collection of insults 23" joke

An intellect rivaled only by garden tools.
An XT clone in a Pentium zone.
Another engineering prototype that should not have been shipped.
Answers the door when the phone rings.
Any slower and he’d be in reverse. - Gignac
As a baby his parents stood him on his soft spot.
As bent as a corkscrew.
As bright as a nightlight / small appliance bulb / tulip bulb.
As happy as if he had brains.
As happy as the village idiot.
As much use as a back pocket in a vest. (Very English.)
As much use as a lead parachute.
As quick as a corpse.
As rare as a nine bob note. (Very English.)
As sharp as a marble / bowling ball / beachball / pin head / wet sponge / bowl of Jello / mashed potato sandwich, and twice as smart.