Calling someone crazy
You’re off your rocker. (informal)
You’re out of your mind. (informal)
He’s two bricks shy of a load. (slang)
You’re out of your tree. (slang)
You’re out of your head. (informal)
She’s out of her skull. (informal)
You’ve lost your marbles. (informal)
You’re crazy. (informal)
You’re nuts. (informal)
They can’t be serious.
You’re a few cards shy of a full deck.(idiomatic)
You’re a few cards short of a deck. (idiomatic)
You aren’t playing with a full deck. (idiomatic)
You’re one sandwich short of a picnic. (idiomatic)
Your front porch light is out.
You’ve gone over the edge.
You’ve gone off the deep end.
You’re nutty as a fruitcake. (cliche’)
Other versions include:
A couple of knights short of a crusade.
Not the sharpest knife in the drawer.
Not the brightest bulb in the box.
Not the brightest crayon in the box.
A day late and a dollar short.
A few beers short of a six-pack.
A few bits short of a byte.
A few clowns short of a circus.
A few screws loose.
Needs another brain to make half-wit.
All wax and no wick.
Nutty as a fruitcake.
Paralyzed from the neck up.
Has a pulse, but that’s about all.
Few bricks short of a load
Two bricks shy of a load