(idiomatic)speak of the devil, talk of the devil, talk of the devil, and he will appear, it is he I was speaking of, of a person who comes just as we are talking about him
De nescioquo loquebaris et subito venit is, dicis tu, 'lupus in fabula'.
You were speaking about somebody or other and all of a sudden that person arrives; you say, 'lupus in fabula.'
De Varrone loquebamur: lupus in fabulā: venit enim ad me.