rabbit hole

Extended senses reference Alice in Wonderland, where Alice travels down a rabbit burrow hole into a bizarre world.

rabbit hole (plural rabbit holes)

1. Used other than with a figurative or idiomatic meaning: see rabbit,‎ hole. (The entrance to) a rabbit warren or burrow.
2. (A way into) a bizarre world.

   These mushrooms will take you down the rabbit hole, man.

   • 1999 March 31, Laurence Fishburne as Morpheus, The Matrix:

     You take the red pill, you stay in Wonderland, and I show you how deep the rabbit hole goes.

3. A time-consuming tangent or detour, often from which it is difficult to extricate oneself.
   • 2017, Judith Aston, ‎Sandra Gaudenzi, ‎Mandy Rose, I-Docs: The Evolving Practices of Interactive Documentary (→ISBN):

     My point is not to go down the rabbit hole of deconstructing the term documentary, [...]

• (way into a bizarre world): looking glass