wackadoo
whacked-out
bananapants
bammy
muckily
cray-cray
crazypants
loco
wiggy
buggish
jiggy
banoodles
gaga
loced out
cray
wackiness
gone fishing
off one's onion
demented
bughouse
crackers
nutzoid
off one's chump
off the beam
meshuggener
not right in the head
hatstand
nutso
off one's rocker
nerts
bugnuts
mad as a March hare
daft
crazy-ass
screwy
bananas
gobaloon
loopy
looney tunes
out of one's mind
off one's head
freakazoid
buggering
toppy
reality challenged
three stops short of Dagenham
loony tunes
nutsy
insane in the membrane
crazy as a shithouse rat