Here's some comments taken from employee reviews.
"Some drink from the fountain of knowledge; he only gargled."
"Wheel is turning, but the hamster is dead."
"She sets low personal standards and then consistently fails to achieve them."
"This person had delusions of adequacy."
"Since my last report, he has reached rock bottom and has started to dig."
"His men would follow him anywhere, but only out of morbid curiosity."
"I would not allow this employee to breed."
"This employee is really not so much of a has-been, but more of a definite won't be."
"Works well when under constant supervision and cornered like a rat in a trap."
"When she opens her mouth, it seems that this is only to change whichever foot was previously in there."
"This employee should go far - and the sooner he starts, the better."
"This employee is depriving a village somewhere of an idiot."
"Got into the gene pool while the lifeguard wasn't watching."
"A room temperature IQ."
"A gross ignoramus -- 144 times worse than an ordinary ignoramus."
"A prime candidate for natural deselection."
"One-cell organisms outscore him in IQ tests."
"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's 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 stand close enough to him, you can hear the ocean."
"One neuron short of a synapse."