Synonyms for Wacky:

adj.

absurd (adjective)
idiotic, screwy.
acting crazy (adjective)
foolish, silly, insane, zany, nutty, daft, absurd, balmy, preposterous, lunatic, loony, demented, nuts, screwy, mad.
amusing (adjective)
comical.
deranged (adjective)
nutty.
foolish (adjective)
imbecilic, cockamamy, tomfool, loopy.
haywire (adjective)
haywire.
insane (adjective)
crackers, balmy, bananas, fruity.

n.

amusing, hysterical, priceless, imbecilic, dippy, nonsensical, knowledge, ability, unearthly, jerky, mad, softheaded, wry, lunatic, absurd, humorous, tomfool, hilarious, dopey, comic, harebrained, comical, playful, moronic, preposterous, cockeyed, idiotic. maniac, cuckoo, maniacal, mentally ill, unsound, brainsick, disordered, distraught, non compos mentis, unbalanced, demented, touched, sane, bananas, screwy, off, moonstruck, Daffy. wacky (noun)
cracked, buggy, around the bend, daft, fool, dotty, cockamamy, cockamamie, kooky, round the bend, nuts, batty, bats, crackers, loopy, loony, haywire, insane, barmy, unreasonable, kookie, goofy, whacky, nutty, loco, balmy, silly, bonkers, foolish, zany, sappy, fruity.

Other synonyms:

mentally ill, jerky, dippy, softheaded, brainsick, bananas, Daffy. maniacal, preposterous, imbecilic, absurd, moronic, lunatic, cockeyed, unbalanced, distraught, non compos mentis, nonsensical, screwy, demented, harebrained. disordered, unsound, moonstruck, idiotic, touched, dopey. mad, unearthly. off. Other relevant words:
demented, bananas, amusing, dippy, distraught, brainsick, comic, imbecilic, absurd, mad, idiotic, lunatic, mentally ill, cuckoo, non compos mentis, preposterous, unsound, screwy, harebrained, hilarious, touched, off, maniacal, Daffy, batty, softheaded, playful, cockeyed, dopey, comical, moonstruck, maniac, unbalanced, disordered, moronic, jerky, tomfool, nonsensical, unearthly.