The secret to their evil is that they manage to be both cute and creepy at the same time. So I'm watching this, and I'm thinking, naturally, "GAAAAAHHHH!!!" but also, "Oh, the poor little thing...someone please help it to the next pond!" That is its power, its evil mind-control power to make you, though fully aware of its evil While. It's. Crawling. Towards. You. feel sorry for it. '
There's another one on YT that shows a giant octopus on the floor of a fish market trying to get away that I just can't watch.