挂羊头卖狗肉(gua沁ngtou mai gourou)
According to Chinese custom,"dog meat is less precious than mutton, and it cannot be served at formal banquets." The saying
literally means a butcher hangs out a sheep's head to attract customers, but it actually sells dog meat. The analogy means people try to attract others with a good appearance, but behave in a completely different way.
Example: Don't trust them. I know the whole lot of them are the kind of people who would hang out a sheep's head, but sell dog's meat.
