Just screw the cabinet closed now its someone elses problem later

Pepper's ghost cat, even.

I'm sure what the joke is here.

There's a joke here, or there's not.

In the reflection, the box appears to have a cat in it. There is no cat in the original (right side) box.

This is a joke on the famous "Schrödinger's cat", a thought experiment about quantum superposition where a cat inside a box is both alive and dead at the same time, up until the moment someone looks into the box.

To me as a layman, this sounds like utter hogwash, so it's funny because it "proves" the experiment as best as it can be proven (which is not at all).

I suspect many theoretical physicists think the same way, but they've learned these equations that tell them they need to believe this hogwash. Let's spare a thought for their troubled souls...