nut-bar
kee siao
fruity
siao
toppy
three stops short of Dagenham
cracky
up the wall
nuts
bonkers
bats
distraught
off one's dot
batty
crazy as a bedbug
daft
mad as a box of frogs
bananas
bugfuck
berko
plumb crazy
round the twist
wud
funny in the head
unglued
gila
nutzoid
off one's trolley
off one's rocker
not right in the head
gone fishing
meshuggener
off one's onion
off the beam
hatstand
doolally tap
bughouse
nutso
off one's chump
crackers
out of one's mind
mad as a March hare
off one's head
gobaloon
becrazed
flip
flip out
one fry short of a Happy Meal
insane in the membrane
mad as a fish