They're an interesting concept, but I find they often overtake the rest of the character's design while the creator is trying to push the tail as a separate entity attached to the character. E.G Mawile does it nicely because that's the whole point of its creature design, it's a mimic

It looks so cheap. I won't buy this company's products anymore if they are cutting corners on their product quality like that.

Eating its liver while it watches