É chamado "E Outra Coisa"

Two characters are in a room having a conversation. One of them makes to leave. But as this character reaches the door, they turn back to deliver a final line. Often this is some bit of exposition that sets up something later in the episode ("the starboard discombobulator's on the fritz") but that the writer couldn't figure out how to work into the scene's main conversation.

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Perfected by Lieutenant Columbo as a means of turning the screw on a suspect who is already exasperated by Columbo's shenanigans, since an Exasperated Perp is liable to make a crucial mistake. Though this became Columbo's most distinctive character trait, it started as a mistake, with two stories on how it came to be. In one, during the filming of the Columbo pilot, "Prescription Murder", Peter Falk simply forgot to deliver his last line before leaving the set, so he turned around, came back, and said "One more thing..." The take was left in, and became a defining moment. In the other, it was the writers that forgot something they needed Columbo to say, so — this being a time of type-writers — rather than start the script page over they threw in "One more thing".