Background: Edward Leo Peter McMahon Jr. (March 6, 1923 - June 23, 2009) was an American announcer, game show host, comedian, actor and singer. McMahon and Johnny Carson began their long association in their first TV series, the ABC game show Who Do You Trust?, running from 1957 to 1962. Then afterwards, McMahon would make his famous thirty-year mark as Carson's sidekick, announcer and second banana on NBC's highly successfully The Tonight Show Starring Johnny Carson from 1962 to 1992.
Context: The pair joined The Tonight Show Starring Johnny Carson on October 1, 1962 on NBC. He describes what happened when the pair first met, the whole meeting being "... about as exciting as watching a traffic light change". For almost 30 years, McMahon introduced the show with a drawn-out "Heeere's Johnny!" His booming voice and constant laughter alongside the "King of Late Night" earned McMahon the nickname the "Human Laugh Track" and "Toymaker to the King". As part of the introductory patter to The Tonight Show, McMahon would state his name out loud, pronouncing it as , but neither long-time cohort Carson nor anyone else who interviewed him ever seemed to pick up on that subtlety, usually pronouncing his name .  Aside from his co-hosting duties, it also fell upon McMahon during the early years of Carson's tenure (when the show ran 105 minutes) to host the first fifteen minutes of Tonight, which did not air nationally. McMahon also served as guest host on at least one occasion, substituting for Carson during a week of programs that aired between July 29 and August 2, 1963, and again for two nights in October 1963. McMahon served as a counter to the notoriously shy Carson. Nonetheless, McMahon once told an interviewer that after his many decades as an emcee, he would still get "butterflies" in his stomach every time he would walk onto a stage and would use that nervousness as a source of energy.  His famous opening line, "Heeere's Johnny!", was used in the 1980 horror film The Shining by the character Jack Torrance (played by Jack Nicholson) as he goes after his wife and child with an axe. He did in-program commercials for many sponsors of The Tonight Show, most notably Budweiser beer and Alpo dog food, and also did commercials for them that ran on other programs.
Question: What caused McMahon to leave The Tonight Show?
Answer: 

Background: Tracey Ullman was born Trace Ullman in Slough, Buckinghamshire, the younger of two daughters, to Dorin (nee Cleaver) and Antony John Ullman. Her mother was British, with Roma ancestry, and her father was a Roman Catholic Pole. On the subject of the spelling of her name: "My real name is Trace Ullman, but I added the 'y.' My mother said it was spelled the American way, but I don't think she can spell!
Context: Along with her television work, Ullman has featured in many films throughout her career. Her first theatrical film was a small role in Paul McCartney's 1984 film Give My Regards to Broad Street. This was followed by a supporting role in the 1985 Meryl Streep drama Plenty. She re-teamed with Streep for 1992's Death Becomes Her, playing Toni, a bartender who runs away with Ernest (Bruce Willis) and lives happily ever after. Director Robert Zemeckis decided to re-shoot the ending, opting for a darker, "more risky ending." This meant that Ullman's scenes would have to be cut. "We were all heartbroken over losing the character. (She) was so great." Despite the cut, some of her scenes were released in an early trailer for the film. Death Becomes Her is one of two instances in which her scenes in a film have ended up on the cutting room floor. Due to time constraints, her song in 1996's Everyone Says I Love You was deleted.  She made her big screen leading role debut in 1990's I Love You to Death acting alongside Kevin Kline, River Phoenix and Joan Plowright. She subsequently appeared in lead and supporting roles in films such as Robin Hood: Men in Tights, Nancy Savoca's Household Saints, Bullets over Broadway, Small Time Crooks and A Dirty Shame. She was nominated for a Golden Globe Award in the category of Best Actress - Motion Picture Musical or Comedy for her work in Small Time Crooks in 2001.  Her voice work in film includes Tim Burton's Corpse Bride and the computer-animated The Tale of Despereaux. She acted as creative consultant on the 2006 DreamWorks feature, Flushed Away.  In 2014, she played Jack's Mother in the film adaptation of the Broadway musical Into the Woods.  Ullman was under serious consideration for a number of roles: Betty Rubble in 1994's The Flintstones; Effie Trinket in The Hunger Games. Director Adrian Lyne asked her to screen test for his film Fatal Attraction. She passed on the idea and the role went to Glenn Close. She was also sought for reuniting with her Plenty co-star Meryl Streep in She-Devil. The part ultimately went to comedian Roseanne Barr.
Question: how long did she act?
Answer:
Her voice work in film includes Tim Burton's Corpse Bride and the computer-animated The Tale of Despereaux.