A person is performing an activity — searching, eating, looking at something, and so on — and as he or she is thus occupied, someone beside or behind them helps them out: pointing out where the object they're looking for is, explaining what they're trying to understand, or making some random comment about whatever they're doing. The person replies, usually distractedly or absentmindedly, with the Stock Phrase of the trope title, or a variation thereof, returning to what they were doing — only to suddenly do a Double Take and whirl around to face X. Usually this would be because X is someone whom they thought was dead, missing, far away, or otherwise impossible to encounter at that place and time.
While this can appear in almost any genre (an especially likely variation is for it to masquerade as a killer Right Behind You in a slasher flick, or some other form of Meaningful Background Event, before revealing its true nature), its origin is actually as a Comedy Trope.
A specific Sub-Trope of Stealth Hi/Bye, where the appearance of the person out of nowhere is always played for laughs and the emphasis is upon the startled character's initial reaction as if nothing is out of the ordinary. Also a subtrope of Delayed Reaction. May be related to Failing a Spot Check. Quite often occurs because a character isn't paying proper attention. Can be a trick the Trickster Mentor or the Eccentric Mentor pulls on his pupil after he has Ascended to a Higher Plane of Existence.
Not to be confused with the rather condescending act of loudly thanking Person B for something minor in order to show Person A, who's watching, how to be gracious.
- Happens in ElfQuest (TOQ #16) when the mysterious muffled figure helping Leetah to heal the dying Cutter turns out to be Rayek, whom she thought had died years before (and had what seemed like evidence to prove it).
- Appears in Batman: Gotham Adventures #1. The Riddler is in his hideout working on a device.
Riddler: Where is my Phillips head screwdriver? (a gloved hand gives him the screwdriver from offscreen) Oh, thank you! (a question mark appears over his head, then he's yanked out of the panel by Batman)
- The archaeologist in The Fifth Element: "Thank you, Aziz!" Aziz was supposed to reflect sunlight at the archaeologist. But the last time he shouted for Aziz, it was actually the Mondoshewan ship, which flooded the room with light, making this a subversion. Aziz was right where he belonged and was expected to be, but not capable of producing that much light.
- A ghost story: A man wakes up in the middle of the night and wishes for light to comfort himself. He reaches for the matches and gets handed a lit one. No one is visible.
- In Discworld, the first book has a bartender committing insurance fraud by burning the bar down. He is handed a match by Death, and the resulting explosion kills him.
- Doctor Who: The Doctor has a rather ridiculous example of this: In "The Pandorica Opens", it takes him minutes to realize he is telling Rory to be quiet and let him think, when Rory was utterly erased from space and time a few episodes ago. He actually exits the scene without noticing, leaving Rory nonplussed, before striding back in with a look of deep confusion to poke Rory in the chest. Of course, considering the nature of the Eleventh Doctor, it was entirely in character.
- In Episode 6 of Umineko: When They Cry this happens when Siesta 410 receives ammo from Gaap
- This happens a lot in the cartoon, especially when Scooby and Shaggy decide to cook or just fool around after splitting up. The monster/ghost makes an appearance handing them something or offering a suggestion before they see it and run for their lives.
- It also happened to Velma when she was in a college lab testing a mummy's bandages to find out if they were really ancient and the mummy handed her a test tube with the right chemical in it. (In retrospect, it's also kind of a clue that the mummy is one of the professors.)
- The Powerpuff Girls:
- In episode "Not So Awesome Blossom", Blossom thanks Buttercup for the kudos for saving the day in the episode while they nosh at a Hot Dog on a Skewer restaurant. Blossom then kvetches that her hot dog has no ketchup (a call back to an earlier scene where a customer rails on her for no ketchup).
- Also, in "Burglar Alarmed", a burglar is stealing from the kitchen while Bubbles goes downstairs for a glass of milk. The exchange happens when she thanks the burglar for the milk and he says "Don't mention it" in return.