Quantum Joke
A joke relating to Quantum Physics and the concept of a joke about Quantum Physics that repeats every cycle of the joke in a loop. The joke itself can be found inside the popular game, Undertale.
So I opened the Quantum Physics book and there, unbelievably, I found another book. This book, however, was a joke book about Quantum Jokes. After flipping that book open I swear to you, there was yet another Quantum Physics book. I don't even know how the books got in each other in the first place. That whole situation turned out to be a real mindfuck.