乖张

Famous false friend: 乖 by itself in modern Chinese means 'well-behaved / obedient' (好乖的孩子 'such a well-behaved child'). But in the compound 乖张, 乖 keeps its older sense of 'going against / contrary', so the whole word means the OPPOSITE — disagreeable and willful.

Literary, slightly old-fashioned. You'll meet it in classical novels (Cao Xueqin uses it for the eccentric 贾宝玉) and in formal character descriptions. In casual speech use 怪 (guài) or 难相处 instead.