Englishaberrant
adjective
Mrs Casper seems to be responsible for Billy's aberrant behaviour:
deviant, deviating, divergent, abnormal, atypical, anomalous, digressive, irregular;
nonconformist, rogue, transgressing;
strange, odd, peculiar, uncommon, freakish, eccentric, quirky, exceptional, singular;
twisted, warped, perverted.
▷antonyms normal, typical.
aberrant Oxford Dictionary of English