The owner found a button on the cat’s back to switch to demon mode
Some cats seem to have some kind of switch on their lower back, at the base of their tail, that switches them into demon mode. You've probably often seen how this happens in various videos on the Internet.
As soon as a person scratches a cat in this area, he begins to make strange sounds, twitch unnaturally and make other non-standard body movements, just like the cat from this video.