Schrödinger's cat is an example of how quantum physics is ridiculously confusing, and makes it easier for the paradoxes be explained.

A subatomic particle either spins clockwise, or counterclockwise, when you look at them, but in actuality, it's spinning both ways at the same time, but the very instant you look, the particle does one or the other.

Schrödinger's cat explains this in simpler terms. A cat is inside of a box with poison gas. The box is sealed from all outside influences (and therefore observers). While the box is closed, the cat is either alive or dead. Once you open the box, the fate of the cat gets "decided." So until the box is opened, the cat is both alive and dead.

Here, the character Schrödinger is a play on that. They clearly shoot her brains all over the place, look away (the key part) and suddenly she's not only alive and well, she's not even there anymore, not leaving even the smallest drop of blood.