Speak of the Devil
WordNet
verb
(1) Mention someone's name who just then appears
WiktionaryText
Etymology
Variation of “Speak of the devil and he shall appear,” which can be traced back to “Talk of the Devil, and he’s presently at your elbow” attested in 1666.
Verb
- An expression sometimes used when a person mentioned in the current conversation happens to arrive on the scene.