Hit every branch falling out of the stupid tree
He donated his brain to science before he was done with it.
Not the brightest crayon in the box.
Few crumbs short of a cookie.
Hiding behind the door when they were passing out brains.
The light is on but there is no one at home.
mad as a hatter?
His oars aren't touching the water.
he is a few fries short of a "happy meal"
Not the brightest bulb in the tanning bed?
One tortilla short of a burrito?