He's a sandwich short of a picnic

The wheel is turning but the hamster is dead.

Intelligent thoughts always followed him, but he was faster.

If he had an idea it would die of loneliness.

I would agree with you, but then we would both be wrong.

Lights are on upstairs but there's no one at home.

His lift doesn't go to the top floor.

He's not the sharpest tool in the box.

He wasn't born stupid, he just got that way with practice.