Synonyms for Kooky:

adj.

bizarre (adjective)
eccentric, ludicrous, ridiculous, weird.
crazy (adjective)
barmy, batty, berserk, cracked, daft, delirious, demented, deranged, fruity, insane, lunatic, mad, maniacal, nuts, psycho, round the bend, screwball, unbalanced, wacky.
deranged (adjective)
nutty.
eccentric (adjective)
crazy.
foolish (adjective)
dotty, irrational, loony, loopy.
insane (adjective)
babbling, batty, berserk, blithering, crazy, delirious, demented, deranged, feverish, frenzied, hysterical, insane, irrational, lunatic, mad, maniacal, neurotic, nutty, psycho, psychotic, schizoid, unbalanced, Crack-brained, brain-sick, crackers, fruity.
kooky (adjective)
bizarre, cranky, curious, erratic, freakish, idiosyncratic, nutty, odd, outlandish, peculiar, quaint, quirky, singular, strange, unnatural, unusual.
lunatic (adjective)
loco, psychotic, schizoid, Fiendish, crackpot, crazy, lunatic, mad, neurotic, nutty.

n.

bizarre, childish, cranky, curious, eccentric, erratic, freakish, idiosyncratic, laughable, ludicrous, odd, outlandish, over-the-top, peculiar, quaint, quirky, ridiculous, rum, rummy, screwball, singular, strange, unnatural, unusual, usual, weird, not in your right mind/not right in the head. kooky (noun)
around the bend, balmy, barmy, bats, batty, bonkers, buggy, cracked, crackers, daft, dotty, fruity, haywire, insane, kookie, loco, loony, loopy, nuts, nutty, round the bend, wacky, whacky.

Other synonyms:

quirky. bizarre, eccentric, freakish, idiosyncratic, outlandish, peculiar, rum. cranky, odd, strange, unnatural, weird. quaint. curious, unusual. erratic, singular. Other relevant words:
around the bend, balmy, barmy, bats, bizarre, bonkers, buggy, cracked, crackers, cranky, curious, daft, dotty, eccentric, erratic, freakish, fruity, haywire, idiosyncratic, kookie, loco, loony, loopy, ludicrous, nuts, odd, outlandish, peculiar, quaint, quirky, round the bend, rum, rummy, screwball, singular, strange, unnatural, unusual, wacky, weird, whacky.