Two characters are in a room having a conversation. One of them makes to leave. But as this character reaches the door, he or she turns 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. In some shows there might be several lines of dialog between the two characters as the departing actor tries desperately not to look as though he's loitering in the doorway.
Just to mix things up a little bit, sometimes they'll do it the other way around: the character who remains in the room will call to the character who's leaving just as the latter reaches the door.
This trope is distinctly different from a good old-fashioned exit line, because the line itself isn't dramatic ("You can't fire me! I quit!") and is often in fact something of a non sequitur, which must be eased into with a phrase like "and another thing" or "by the way."
Sometimes a character actually gets out the door, then comes back in to deliver a line, but this is usually for comedic effect. See
Door Focus.
Example:
- Perfected by Detective 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. 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.
- Likewise, Detective Goren from Law & Order: Criminal Intent, also uses And Another Thing in the same way as Columbo did.
- The medical version (the "doorknob question") appeared in House: according to the writers (and presumably their medical consultants), many patients come in for a trivial ailment, and then bring up the "other thing" (probably the serious illness they actually want treatment for, but which embarrasses them) as they reach for the door knob.
- This trope was parodied mercilessly on South Park with a scene that ended in four successive And Another Things. Clone High did the same in in the premiere, as JFK kept coming back into the bathroom to reiterate the fact that Lincoln and Gandhi weren't invited to his party, and then because "I forgot to wash my hands!"
- Uncle from Jackie Chan Adventures easily established "One more thing!" as one of his catchphrases by the end of his first scene in the series.
- Real Life example: Steve Jobs' keynote presentations for Apple Inc. often end in "one more thing" that didn't quite fit into the presentation itself.
- Detective Flack did this once on CSI NY. When he made to leave, the door gave him a Creek Moment - he realised that the victim's door had been locked from the outside, so whoever killed him must have had a key.
- Star Trek The Next Generation often raised this to an art form, with whoever Picard was talking with in the ready room would say that one more thing at the door.
