rabbit hole

noun4

1. •
   (figurative) A bizarre world, where everyday rules do not apply.
2. •
   (figurative) A time-consuming tangent or detour, often one from which it is difficult to extricate oneself.

   • I'm also a fan of a really obscure book series, but that's a rabbit hole that we won't get into.
   • While writing my paper, my research went down several rabbit holes that were only marginally related and wasted a lot of my time.
3. •
   (figurative) A way into such a world.

   • These mushrooms will take you down the rabbit hole, man.
4. •
   (figurative) The initial clue that leads to an alternate reality game.