New slang： Speak of the devil.
someone appears after you mention them. "Speak of the Devil" is short for "Speak of the Devil and he shall come". It was believed that if you spoke about the Devil it would attract his attention. That's why when you're talking about someone and they show up people say "Speak of the Devil".
刚刚提到某人，某人就出现。以前的传说是如果你提到魔鬼，魔鬼就可以听到，同样的，你提到一个人，一个人就出现，那么就可以说speak of the devil。
所以下次，当你谈到某人，某人就正好出现时，你就可以说Speak of the devil. 或是Talk of the devil.