The Box (real)

The Box is a mysterious box found in a cutscene after Night 7 in FNAF4. It hasn't been opened, and it has been said to have the pieces put together.

We don't know what's in the box, or even how to open it, as it's not possible to do so in the games. However, since canon has integrated into World Prime, we're pretty sure the box does, in fact, exist somewhere.

There have been several "sightings" of this box in the The ETQAY Saga, but both the first and second iterations have been proven to be fake. The third iteration may or may not be the real box.