You can tell by the look on its face that this cat has no idea what the hell is going on. It's the same effect as when you put a piece of tape on a cat's head or back of the neck. Their mind can't computer the existence of piece of tape on their back, so they just think something is pressing down on them. It's hilarious, but also torturous. That's the definition of a prank, isn't it?
This little girl is getting a kick out of a cat wearing a hat. You have to lob the simplicity of a child's mind. Sometimes we as adults tap into that, but it's very difficult. When's the last time you laughed hysterically at something very simple. Watch an old Warner Brothers cartoon and have yourself a good old fashioned child laugh.