That Mysterious Thing

"Potamus: Did'ja get that thing I sent ya? Birdman: No! No I didn't! I never get 'that thing' you sent me! I've never gotten that thing you sent me, and I'm beginning to wonder if you ever sent me anything! While I'm at it, if I had gotten that thing you sent me, ever, I doubt I'd be interested in what it said."

- Harvey Birdman, Attorney at Law

Sometimes characters will refer to an object, person, event or plan in an extremely ambiguous way, mostly just to screw with the audience. Maybe it's a Running Gag, which will never be revealed, because to do so would ruin a perfectly good joke. Maybe you're seeing events from a particular character's perspective, and because it is integral to the plot that this character doesn't know what this 'thing' is, other people with refer to it in vague terms so as to heighten the suspense and not give away the ending. Maybe it's the cake for a surprise birthday party. Maybe it's a priceless artifact another character is planning to steal. Either way, you won't know what that mysterious 'thing' really is until the most dramatic moment possible.

See Noodle Incident ("Remember 'that time' when..."), Noodle Implements ("'That thing' I plan on doing with all this weird stuff..."). May turn out to be a Chekhov's Gun, involving Foreshadowing. Occasionally related to Buffy-Speak, when a character refers to something as a 'thing' due to lack of full knowledge of what said 'thing' actually is. Compare Hurricane of Euphemisms and related tropes, in which the mysterious 'thing' isn't referred to vague terms but in bizarre ones. Not to be confused with You Know That Thing Where or The Thing That Goes Doink.

Anime and Manga

 * The "new recruits" mentioned in the first episode of the second season of Ghost in the Shell: Stand Alone Complex.

Film

 * In the movie and play Doubt, character go out of their way, understandably, to not say the words 'gay' or 'molestation'. They don't even say 'homosexual', which would be the most likely word for that time and place. The closest they really get to saying it out loud is 'the boy's nature' and 'inappropriate relations'. It's actually pretty interesting how they get everyone in the audience to know what they are talking about immediately, without actually putting a name to it.

Literature

 * In Mercedes Lackey's Owl Trilogy from the Heralds of Valdemar Series, in the second book, everyone dances around the name of the person who is going to be his mage-teacher, simply referring to him as 'your teacher' until they surprise him with the incredibly famous (or infamous) Firesong, only the most powerful mage in the freaking world.
 * In Harry Potter and The Philosopher's Stone, Hagrid tells the bank goblin, "I'm here to pick up the you-know-what in vault you-know-which." It turns out to be the Philosopher's Stone.

Live-Action TV
""The Watch will be ready for you at midnight. The watch. The Chinese watch...""
 * Monty Python's Flying Circus did this a few times.
 * Nudge, Nudge, Wink Wink sketch is mostly about this.
 * Another sketch has the British government debating taxing "thingy".
 * In the Pirhana Brothers sketch, with a mobster being interviewed by a reporter, and trying to keep a transaction secret:

Music

 * "The Thing" by Phil Harris. The song is called "The Thing" but the word Thing doesn't actually appear in the song - it's just BOOM BA-BOOM.
 * "I Got It From Agnes" by Tom Lehrer.
 * "One Thing" by Finger Eleven. Apparently he'd trade it all for that one thing, whatever it is.
 * Alternatively, he's trying to find something that would be worth trading away everything else.

Web Comics

 * In Darths and Droids, Pete has a die that is this. We don't know what its made out of, but its apparently unsafe to roll indoors, must land on a metal tray, and is possibly deadly.

Western Animation

 * From Harvey Birdman, Attorney at Law, 'That thing' that Potamus always sends people.

Real Life

 * In Real Life the Manhattan Project created the first atomic bomb. Most people in the Project had no idea what it was making. But for the few who did, they often referred to the bomb as "the gadget" for security reasons.