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

For further exploring for "screwy" in Webster Dictionary Online