Basically there is a biblical phrase that reads "Speak of the devil and he shall appear." This saying is now used as an idiom when you speak of something or someone and then they unexpectedly show up. For instance, if you were talking on the phone with a friend, and start talking about something a third friend did, then you hear someone knock on the door, you look out and see that third friend, you would might say "Speak of the devil.." Despite the reference to the devil, this phrase does not generally carry a negative connotation by default. Simply a display of the coincidencal appearance of the person or thing being spoken about.

hellopanda77说的没错 注意哦， 是 speak of the devil 而不是 speaking. 完整的句子是， Speak of the Devil and he will appear Edit - @ hellopanda77, it sounds like you would be correct but I'm afraid not. "Speak of the devil, here comes INSERT NAME OF PERSON YOU WERE JUST TALKING ABOUT" it doesn't have to be someone you dislike. Just the same person you were talking about.

the one you talk about with someone just appeared.

说曹操曹操到。

“说曹操曹操就到了” Note: 可是应该也可以用speaking吧 as present progressive: speaking of the devil (as you were just barely talking about him/her), here comes INSERT NAME OF PERSON YOU DISLIKE. dunno, makes more sense grammatically.