No wonder he reacted so badly that time he was heckled.
James Masters as Spike on Buffy and Angel was my first thought. Not only did he do a very convincing Cockney accent (with coaching from Anthony Stewart Head), but he had some really nasty early scenes, along with some very intensely emotional scenes later in the series. He’s a California Dude off-screen. I was impressed with how effortless he made it all seem.
I just finished watching a retrospective on The Red Green Show. Was completely taken aback by how different Steve Smith’s real voice is. But at least he looks the same in or out of character. When Patrick McKenna came out on stage as himself, I flipped. I think it’s not just the hair and the glasses; he actually twists his face to play Harold.
(Actually, I shouldn’t have been that surprised; I’d seen an episode or two of Traders, back in the day, and I saw the TV version of The Music Man where he was the anvil salesman. Still, dang.)
Kavner’s natural voice (jump to 1:11) is a lot smoother than Marge Simpson’s.
One surprising counter-example is Dan Mintz. Mintz is one of the writers for Bob’s Burgers and he also does the voice for Tina.
I had always assumed that he was doing a highly exaggerated voice for Tina. So I was astounded when I saw him in an interview and found that it’s pretty much his normal voice.
Wow, what a surprising interview… I don’t think I ever gave Goldthwait credit for that much depth.
Robert Carlyle in Once Upon a Time… he plays one character (Rumplestiltskin) in numerous unique forms. The flamboyant, gold-skinned Dark One (cursed-Rumplestiltskin) standing out, the most.