WordNet (r) 3.0 (2006):

kooky
    adj 1: informal or slang terms for mentally irregular; "it used
           to drive my husband balmy" [syn: balmy, barmy,
           bats, batty, bonkers, buggy, cracked,
           crackers, daft, dotty, fruity, haywire,
           kooky, kookie, loco, loony, loopy, nuts,
           nutty, round the bend, around the bend, wacky,
           whacky]

Moby Thesaurus II by Grady Ward, 1.0:

123 Moby Thesaurus words for "kooky":
   abnormal, absurd, anomalous, apish, asinine, balmy, bananas, barmy,
   bats, batty, beany, befooled, beguiled, besotted, bonkers,
   brainless, buffoonish, buggy, bughouse, bugs, cockeyed, crackers,
   crank, crankish, cranky, crazy, credulous, crotchety, cuckoo,
   curious, daffy, daft, dazed, deviant, deviative, different, dippy,
   divergent, dizzy, doting, dotty, dumb, eccentric, erratic,
   exceptional, fatuitous, fatuous, fey, flaky, flipped, fond, fool,
   foolheaded, foolish, freaked out, freaked-out, freakish, freaky,
   fruitcakey, fruity, fuddled, funny, futile, gaga, goofy, gulled,
   haywire, idiocratic, idiosyncratic, idiotic, imbecile, inane,
   inept, infatuated, insane, irregular, just plain nuts, kinky,
   loony, loopy, mad, maggoty, maudlin, moronic, nuts, nutty, odd,
   oddball, off, off the hinges, off the track, off the wall, out,
   outlandish, passing strange, peculiar, potty, quaint, queer,
   quirky, round the bend, sappy, screwball, screwballs, screwy,
   senseless, sentimental, silly, singular, slaphappy, strange,
   stupid, thoughtless, twisted, unconventional, unearthly, unnatural,
   wacky, weird, wet, whimsical, witless, wondrous strange