I LOVE your description of that guy, josepp! ;-D Yes, I've seen the odd act that was about that bad at open mikes here and there. I've even seen acts that KNEW they were terrible and they did it just to play the fool, but the ones who DON'T know they're terrible but think they are great are fairly rare, fortunately.

Someone should put together a video showing several such performers and release it as a musical comedy.