The two have appeared in 21 and 28 episodes respectively Mantegna also appeared in the film. Actor Kelsey Grammer first appeared as Sideshow Bob in the first-season episode "Krusty Gets Busted" while actor Joe Mantegna made his first appearance as Fat Tony in the third season episode "Bart the Murderer". McClure and Hutz were subsequently retired from the show. He voiced the recurring characters Troy McClure and Lionel Hutz as well as numerous other one-time characters, until his death in 1998. Edna Krabappel was then retired from the show, but sometimes appears as a ghost, and actor Phil Hartman guest-starred in 52 episodes, more than any other male actor, although his initial role in the second season episode "Bart Gets Hit By a Car" in 1991 was intended to be a one-off. Actress Marcia Wallace guest starred 176 times, making her the most recurring female guest star on the show, until her death in 2013. Several guest stars have made multiple appearances on the show, often as recurring characters. Singer Tony Bennett was the first guest star to appear as himself, appearing in the season two episode "Dancin' Homer" while Aerosmith were the first band with their cameo in the third season's "Flaming Moe's" The first male guest star was actor Sam McMurray, who voiced a worker at the Springfield Nuclear Power Plant in "Homer's Odyssey", the show's third episode, and Marcia Wallace was the first female guest star on the show starting from Bart the Genius as Edna Krabappel and Ms. In the earlier seasons, most of the guest stars voiced characters, but eventually more started appearing as themselves. Guest voices have come from a wide range of professions, including actors, athletes, authors, musicians, artists, politicians and scientists. Kevin Michael Richardson started as a recurring guest star in the twenty first season, but joined the supporting cast in the twenty eighth, starting with the episode "The Last Traction Hero". Guest stars have appeared on The Simpsons since its first season, in addition to the show's main cast of Dan Castellaneta, Julie Kavner, Nancy Cartwright, Yeardley Smith, Hank Azaria and Harry Shearer and supporting cast of Tress MacNeille, Pamela Hayden, Maggie Roswell, Chris Edgerly, Grey Griffin, Alex Désert, Eric Lopez, Tony Rodríguez and former supporting cast members Russi Taylor, Marcia Mitzman Gaven, Karl Wiedergott, Doris Grau, Jo Ann Harris, Susan Blu and Christopher Collins.
As of April 18, 2021, there have been 898 guest stars on the show, with this figure rising to 902 if The Simpsons Movie is included.
The show was awarded the Guinness World Record for "Most Guest Stars Featured in a TV Series" in 2010. Grammer, Mason and three-time guest star Anne Hathaway all won the Primetime Emmy Award for Outstanding Voice-Over Performance for guest voice roles on the show. Three guest stars, Ricky Gervais, Seth Rogen and Pete Holmes, earned writing credits for the episodes in which they appeared. Simmons, Sally Stevens, George Takei and Michael York have made over five appearances. Greene, Valerie Harper, Jan Hooks, Jane Kaczmarek, Stacy Keach, Kipp Lennon, Dawnn Lewis, J. Mantegna has appeared over thirty times, Grammer, Maurice LaMarche, Jon Lovitz and Frank Welker have appeared twenty times or more Glenn Close and Jackie Mason have appeared over ten times, while Albert Brooks, Michael Dees, Dana Gould, Terry W. After Wallace, Hartman made the most appearances, guest starring 52 times. Several guest stars have featured as recurring characters on the show, including Phil Hartman, Joe Mantegna and Kelsey Grammer. Singer Tony Bennett was the first guest star to appear as himself, appearing briefly in the season two episode " Dancin' Homer". The first credited guest star was Marcia Wallace who appeared in " Bart the Genius" in her first stint as Bart's teacher Edna Krabappel. In the show's early years most guest stars voiced original characters, but as the show has continued the number of those appearing as themselves has increased. Actor Phil Hartman, who died in 1998, was the most recurring male guest actor on the show, appearing 52 times.