Vivien wrote:the lights are on but there's no one home (stupid/thick/dim/weird)
Oh, I've heard so many variations on that theme!
The cheese has slid off his cracker.
A few fries short of a Happy Meal.
Not the sharpest knife in the drawer.
The wheel's spinning but the hamster's dead.
Elevator doesn't go all the way to the top floor.
A sandwich short of a picnic.
And on and on!