Wild
Out there
Wacked
Wacko
Out of it
Psycho
To be wacked out
Crackers
To go crackers
Off their rocker
Gone off their rocker
Not wrapped too tight
A couple of fries short of a Happy Meal
The lights are on, but nobody's home
Off your trolley
Out of your tree (and running loose in the park)
Not the full shilling
A couple of sarnies short of a picnic
Cookoo
Gone bananas
Away with the faeries
Talking to the faeries
Linked to the Moon
Bokers
A couple of snags short of a barbie
Got kangaroos in the top paddock
A few bricks short of a load
Bats in the belfry
Out to lunch
Cracked
Lost their marbles
Out of their mind
Certifiable
Belongs in the funny farm
Has a few screws loose
As mad as a hatter
Around the bend
Full tilt bozo
Thrown a wobbly
One beer short of a six-pack
One sandwich short of a picnic
Nutty as a fruitcake
A few screws loose
Mad as a March hare
Funny in the head
You're wired-up wrongly
You have the brain in neutral
You have a loose connection up top
You have bats in the attic
You have rots in the loft
You're batty
You're knitting on only one needle
You haven't got both oars in the water
You're one match short of a test
You're one stump short of a wicket
You're one beer short of a round
You're one innings short of a match
You're one ball short of an oven
Elevator doesn't go all the way to the top
Not all there
Crazy like a fox
Went to have lunch early