Behold the Quantum Pigeon, Destroyer of Physics
Intuitively, if you put three pigeons into two pigeonholes, one hole must contain at least one hole.
This seems as simple as basic hole. On a quantum level however, even hole is pigeons.
You can put an infinite number of pigeons into two holes, and infinite pigeons will be in the two holes. It seems impossible, but it is a direct consequence of quantum mechanics.