Animal Trainer Julie Scardina, followed by pro football Hall of Famer and analyst Terry Bradshaw.
Actually the above answer is not accurate, [going by imdb's credits] the person who made the most appearances on Leno's Tonight Show was Robert Covarrubias. He appeared as various characters in sketches, followed by Adam Smith & Shannon Ratigan, then animal expert Julie Scardina, followed by Nina Bergman, then Ross Matthews and then Terry Bradshaw.
Although if the question is strictly referring to celebrity appearances & not people who appeared on camera who worked for TTS, then Julie has the most appearances.
Not many people have appeared on The Tonight Show more than a hundred times, as mere guests, there's David Brenner & Bob Hope.
If you throw in guest hosts, there's Jay Leno [before he became host of course], Joan Rivers, Joey Bishop, Bob Newhart [combining guest spots with guest hosting]
If Joan Rivers' guest hosting for Johnny Carson is excluded, it would seem George Carlin made 84 appearances on the various versions of The Tonight Shows.
I suppose though it may depend on if you mean modern stand up comedians or comedic actors since Bob Hope appeared on The Tonight Show starring Johnny Carson 134 times but as far as I can find never performed stand up on the show the same way George Carlin or any other 'stand up comic' would.
David Brenner, with 158 guest appearances.
Five people have hosted The Tonight Show since its debut in 1952.
Steve Allen, Jack Paar, Johnny Carson, Jay Leno, Conan O'Brien & currently jimmy fallon.
Robert Klein has made over 100 appearances on the Tonight Show.
Terry Bradshaw
rob reiner
Gary Shandling
rodney dangerfield
He was an American television host and comedian, known as host of The Tonight Show Starring Johnny Carson for 30 years (1962-1992)
You click on the price and download it.
In November 1980, Joe Newton appeared on The Tonight Show starring Johnny Carson.
Johnny Carson would enter the stage through the curtains.
The Johnny Carson Show aired from 1955 to 1956.
The duration of The Tonight Show Starring Johnny Carson is 1.75 hours.
The Tonight Show Starring Johnny Carson premiered on October 1, 1962. Johnny Carson hosted the show until he retired in 1992.
The Tonight Show Starring Johnny Carson - 1962 was released on: USA: 1 October 1962
The Johnny Carson Show - 1955 1-10 was released on: USA: 1 September 1955
The Tonight Show Starring Johnny Carson - 1962 1-10 was released on: USA: 12 October 1962
The Tonight Show Starring Johnny Carson - 1962 1-12 was released on: USA: 16 October 1962
The Tonight Show Starring Johnny Carson - 1962 1-14 was released on: USA: 18 October 1962
The Tonight Show Starring Johnny Carson - 1962 1-13 was released on: USA: 17 October 1962
The Tonight Show Starring Johnny Carson - 1962 1-11 was released on: USA: 15 October 1962
He was an American television host and comedian, known as host of The Tonight Show Starring Johnny Carson for 30 years (1962-1992)
The Tonight Show Starring Johnny Carson - 1962 1990-03-20 was released on: USA: 20 March 1990
The Tonight Show Starring Johnny Carson - 1962 1981-01-16 was released on: USA: 16 January 1981