兽面人心人面兽心
[shòu miàn rén xīn rén miàn shòu xīn]
A play on a proverbial phrase. 'The first part, Beast's face but human's heart, refers to someone who may not be good-looking but has a kind heart; The second part, Human's face but beast's heart, refers to hypocrites who appear friendly but are ill-natured.'