Stephen Colbert stays in character most of the time.
Super Dave Osbourne?
Johensen was frontman of the New York Dolls, not Television. 
Beat ya to it!
Chuck Knipp, an obese white male nurse and Quaker Universalist minister, is best known publicly (particularly in gay bars) as Shirley Q. Liquor, a fat ghetto-philosopher black woman famous for her monologues (the Titanic Reprise link on that page probably being the most famous- politically incorrect but I can’t pretend I didn’t laugh until there were tears in my eyes the first time I heard it). He gets hate mail and mobs of picketers at his appearances from both blacks and whites protesting his blackface personal appearances and at the same time has rabid fans, again both black and white, who call him a comic genius on par with Lily Tomlin or Whoopi Goldberg (the latter being one of his biggest fans).
Pat Harrington, bka Schneider from One Day at a Time, was originally famous in the 50s/60s as Guido Panzini, an Italian playboy and bon vivant who made occasional appearances on Arthur Godfrey and other shows. He also reprised the role once in a “lookalike” episode of ODaaT. Speaking of Guido alter egos, there’s also Don Novello who occasionally acts under his own name but is best known as Vatican gossip columnist Father Guido Sarducci.
Dopers over 35 may remember Murray Langston, best known as The Unknown Comic on The Gong Show and a mini-career on other shows.
While it was a one time only gig, Andy Kaufman introduced his elderly Jewish grandmother at his famous “cookies and milk” concert and had her sit on the stage where she looked senile and confused. At the end of the concert Grandma took off her make-up to reveal that she was really Robin Williams in pre-Mrs. Doubtfire old lady drag. Also speaking of Kaufman, Tony Clifton has been played by at least four people over the years (Kaufman, his brother, Bob Zmuda, and an unknown accomplice who made appearances at Kaufman shows upon occasion to screw with the audience.
Has he ditched the props? If so, does he tour under his real name? I would think that’d help.
Woah! Is he the “Albanian” guy from the Handsome Boy Modeling School albums?
I was a security guard on that show and found him very low key when the cameras were away from him. Quiet, polite and at times even seemed almost contrite. Could have been his true nature or just sorta evolved that way after very high high and then the inevitable lull that followed.
On the flip side, Moonwife cleaned Howie Mandel’s teeth once and thought he was such a kick in the pants she insisted he should try his hand at showbiz (“Nah, I’m just an electrician; thanks anyway.”) He’s not far from his on-screen persona even when he’s off-camera – which might surprise some. FWIW, I think Mandel one of the great comics of our time, doesn’t get his fair due and should be getting meatier work.
Umm, pretty good source (waited on him a lot at a place in the Valley) tells me Dean Martin actually did drink daily and a lot.
According to Wiki, Raymond Burr fabricated a dead wife and child to avoid being outed.
Well, he couldn’t rein himself in for the famous November 12, 2003 CNN interview by Allen Chernoff, (partial transcript) which suggests poor judgement, at least.
I can’t believe I missed this one. Ed Zotti is really a character played by Lynn Bodoni.
I also can’t believe I didn’t remember Don Novello/Guido Sarducci.
Robin Williams has a quiet, mature alter ego. Like Steve Martin, he has managed to put the “wild and crazy guy” behind him.
Bob Saget. He had that squeaky clean, Full-House-Americas-Funniest-Home Videos persona, whilst being the foul mouthiest stand up comedian.
Groucho Marx and Dolly Parton are two celebrities who pass(ed) unnoticed among their fans by simply dressing as themselves. (For Groucho this was in the era when he wore greasepaint or otherwise false moustaches; Dolly’s without huge hair and gobs of makeup and industrial strength support bras is supposedly unrecognizable- she once sent in her photo to a Dolly Parton lookalike contest and didn’t make the first cut.)
Wow. I would’ve figured even without the hair and spackle that Dolly and the Twins would be hard to mistake.
I don’t know if this counts, but Maynard James Keenan (lead vocalist of Tool) has done the same thing. He has worn some pretty crazy stuff on stage that renders him near unrecognizeable. He related a story in one interview where he was talking with the guitarist after a show and, as he walked away, some fans ran up to him and said “Hey, were you just talking to the guitarist from Tool? Do you know him?”
From what I am led to believe, Marilyn Manson is actually a pretty erudite, quiet guy when he’s not in the make-up. Totally knows how to manipulate his image, too, to get as much ‘shock’ value as possible.
The ones I wonder the most about are probably Gilbert Gottfried and Bobcat Goldthwait, two people whose last names I have no hope of spelling correctly. Also, what’s Mr. T like when he’s not on camera?
Mitch Hedberg’s on-stage persona was mostly an act. I saw one performance where he said something like “Uh oh, that sounded a little too close to my real voice. I may have to kill you all now.” If you want to hear his “normal” voice, watch the episode of “Home Movies” where Brendon has to babysit a cat; Mitch is the guy giving the eulogy for the cat at the end. He talks a lot faster, and it’s nothing like his slow-paced stoner persona.
I always get the feeling that Paris Hilton’s a much smarter cookie than her public persona would have you believe. I’ve read in magazine articles that in private, in person, she doesn’t talk with that high, breathy, little-girl voice; she herself has said something along the lines that it takes a pretty smart girl to play such a dumb blonde for so much money.
Minnie Perle and Grandpa Jones (is that right?) from Grand Old Opry. My dad said he saw Grandpa Jones perform after WWII when he was probably in his 20s and he was still “Grandpa”