He has a teflon brain (nothing sticks).
He's like uncultivated woodland. Totally dense.
He's got a photographic memory, but the lens cap is on.
He's sausage short of a barbecue.
He's a renewable energy source for hot air balloons.
You're the kind of person I can't get over, so I'll go around you.
I feel sorry for your little mind - being all alone in that great big head.
I'd insult you, but you're not bright enough to notice.
He has an answer to every problem. It's a shame they are always the wrong answers.
He is a man of many parts, it's just a shame they were put together so badly.
I wish you were all here. I don't like to think there is more!
People may say that you are the perfect idiot. I must say that you are not perfect, but you are very close to being.