"Speak of the devil" neutral-sounding synonym for non-person scenario
speaking of [substitute a noun]. If you are surprised by the arrival of something or someone, regardless of what it is, you may use /speaking of + noun/ "Speaking of planes, look John, there it is". "Speaking of friends, ours have just arrived." "Speaking of grammar, I knew there'd be a question about that."
Perhaps, As I/you/he/she/we/they were saying... or, And right on cue... .