madman, madwoman

abnormal, deviant

manic-depressive, monomaniac, mythomaniac, neurotic, obsessive, obsessive-compulsive, paranoid, psychoneurotic, psychotic, schizo, schizoid, schizophrene, schizophrenic, sociopath

character, codger, crack, crackpot, crank, eccentric, fantastic, flake, kook, oddball, oddity, original, quiz, screwball, tyke (also tike) [chiefly British], weirdo, zany

case, patient