Noodle Incident/Tabletop Games

The Noodle Incident is an important part of tabletop RPG design, giving the games master ways to use his own ideas without going against canon.

Deadlands explicitly invokes this trope in some adventures. For example, Canyon O'Doom includes a scene where the characters discover a deserted town and a frightening suicide note. The adventure notes state that there is no actual resolution to the scene, that not everything in the Weird West makes sense, and that sometimes the unknown is the scariest thing of all.
During the second Penny Arcade and PVP Dungeons & Dragons 4th edition podcast, the motive for Acquisitions Incorporated is recovering from "the Winterspire Incident." All we are told by the DM is that "it was pretty bad."
In Changeling: The Lost, you'll find this gem. "Changelings tend to avoid giving Freeholds too-obvious names derived from myth, ever since the disaster that befell the 17th-century legendary freehold of New Lyonesse."
- There's a hint if you study Arthurian legend. Lyonesse is the home country of Tristan. In later versions of the story, it's said to have sunken beneath the sea...
- Genius: The Transgression has a few, up to and including the reanimation of Pythagoras.
Dungeons & Dragons
- The Splat Book Greyhawk Adventures from the original Advanced Dungeons and Dragons contains many spells designed by the Circle of Eight; most, that is. The narrator claims that there are no 8th or 9th Level spells, as those were too well protected for the scribe to put to paper. The narrator also mentions spells like Drawmij’s instant stripping and Otto’s gelatinous cube transformation into edible gel that were omitted because those were “too esoteric for even the most curious spell crafter.”
- The 3.5 sourcebook the Player's Handbook 2 includes a sample quote in the Bard character archetype section: "This reminds me of the time Prince Voltred tried to enter his falcon in the archery contest. Funny thing about that..."
In Shadowrun Dunkelzahn's Will contains approximately 20% various noodle incidents the dragon has seen fit to clean up after following his death.

To Alamais, I leave the fruitcake we have exchanged every Christmas since 2020. Unlike you, I’m really dead.

Vampire: The Requiem has the origin of Vampires as a permanent mystery
The exact nature of The Mourning in Eberron and its causes is also a permanent mystery.
- For that matter, the Eberron setting does this a lot, leaving a lot of details about major events and personalities vague so that the DM can fill it in to suit his campaign's needs. For instance, nothing is known about the identity, motivations, or background of the Lord of Blades, often regarded as the Big Bad of the setting; all that is truly agreed on is that he is a Warforged, but as the information in the link shows, there's even some doubt of that.
Then there's this rpgnet thread, which contains more than a hundred. At present, the first post contains the phrase "In case of vampire attack, all my underwear goes to the man with the strongest chin", the latest^[when?] post has "Wait, I've got four ranks of Knockback. I punch the elephant back into the clown-car", and things are even weirder in-between.