镜子里的人好帅你要点脸再说话
[jìng zi lĭ de rén hăo shuài nĭ yào diăn liăn zài shuō huà]
Literally translating to 'The person in the mirror is so handsome, you should have some shame before you speak.' This suggests the person is arrogant and should be modest. This is likely used in jest towards someone who is vain or boastful.