Somebody collected a bunch of clips showing cats reacting to their owners using the cat filter on their computer. It's usually the same setup. The owner sits at the computer, and they have the cat on their lap facing the screen.
When the filter is turned on, the cats are completely confused. Their eyes get wide, some look back and forth to see if there really is a giant cat head behind them. One tries to bite its owner, and another is so shocked it falls to the floor.