complementando as sugestões acima:
speak of the devil (and in he walks), and Talk of the devil (and he is sure to appear).
Prov. Talk about a certain person, and that person appears. (Used when someone appears whom you have just been talking about.)
Alan: I haven't seen Bob for weeks.
Jane: Look, here comes Bob right now.
Alan: Well, talk of the devil. Hi, there. We were just talking about you. speak of the devil and in he walks.
Apparently, Lisa went there and wasn't very impressed - oh, talk of the devil, here she is.
Well, speak of the devil, here's Patrick now.