This is a subtrope of Game-Breaking Bug, but it is completely harmless, and even fun... until you do EXACTLY THE WRONG THING. It is named for a glitch in The Legend of Zelda: Phantom Hourglass where you can walk through walls. However, that makes it possible to fall into an inescapable area inside the fence around Oshus's house. If you save there, the game becomes unwinnable. Subtrope of: Game-Breaking Bug Unwinnable by Mistake Unwinnable by Insanity (occasionaly, if done deliberately.)
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Three days must pass before this YKTTW is Launchworthy or Discardable