Synonyms for Kooky:

adj.

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

n.

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

Other synonyms:

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