I think he got over because he was an Elvis impersonator... that's instant heel heat right there.
Some others -
Rikishi (I know Too Cool has been mentioned, but there was a time where Rikishi had white hot heat)
Al Snow in ECW - I know ECW is a bit different, but the whole "Head" angle was super hot.
The New Age Outlaws - I know Road Dog had the charisma, but you have to think that the level of popularity the team had wasn't planned.
Snow worked in ECW because the angle was tailor-made for a smart audience.
I never got why Kaientai got over during their EVIL~! INDEED~! era. They were very dull in the ring, and their voiceovers were lame.
La Parka's voiceover was much cooler.