When a TV show starts trotting out guest star appearances, it's usually an effort to boost low ratings. But when it comes to The Simpsons, it's more than that. In fact, The Simpsons has actually poked fun at how TV shows so shamelessly use guest stars.
Guests stars on The Simpsons aren't just there to be gimmicks. They often take up interesting roles that impact the show in important ways—even when they don't have too much screen time.
The best guest stars on The Simpsons have left indelible marks on the show's legacy and its fictional residents. Here are some of the most memorable guests to appear on The Simpsons!
8. Johnny Cash
"In your face, Space Coyote!"
Homer's admonishment of his spirit guide as he realizes that Marge truly is his soulmate? A great line. One that comes from delight as he stands in a lighthouse, having bettered his inner voice.
The voice of Homer's Space Coyote is none other than Johnny Cash. He lends his vocals to a being who appears before Homer after consuming too many "death chilies." He tells Homer to find his soulmate, then attempts to gnaw on his leg.
Cash's role was wonderfully fun as he embraced being an animated coyote with gusto. He gave Homer a spiritual journey to embark upon so that he can be sure of who his soulmate really is: Marge.
7. Mickey Rooney
It may have been brief, but Mickey Rooney's appearance in The Simpsons was full of baffling humor.
When Milhouse goes into hiding because he doesn't want to be an actor, Rooney is choppered in, lands in Bart's treehouse, and tries to convince Milhouse back to the set. He's unsuccessful—and attempts to take the role of a child superhero sidekick for himself.
Mickey had fun doing the vocal work, and his role was hilarious from start to finish. The best moment comes when Rooney tries to get through to Milhouse by telling him to do it for the fans, the foreign markets and, most of all, for himself "the Mickster"!
6. Ernest Borgnine
When Bart joins the Junior Campers, he heads out on a father/son retreat with Homer. However, one of the camper's father is in prison, so Ned Flanders organizes a "special celebrity Dad" to fill the void.
Enter Ernest Borgnine, whose appearance was brief but hilarious.
His bombastic attitude and attempted consoling of the child he's supposed to be looking after are priceless—as is the look of fear when he realizes that he can't stop a bear from attacking them because Homer has stolen his pocket knife.
Borgnine's character tries to protect the kids throughout the episode, but in the end dies to an unseen presence in the woods. His time on screen was funny, wacky, and egotistical, which makes the humble Hollywood actor one of the best guest stars in willing to mock himself.
5. Michael Jackson
During the catastrophic events that follow Bart's decision to wash his red hat with the white laundry and accidentally turn Homer's shirts pink, Homer ends up in an asylum.
While there, he meets Michael Jackson—who voices the person of Leon Kompowsky, a bricklayer who ended up in the asylum for thinking that he's Michael Jackson.
The hilarity of the episode is that Homer has no idea who Michael Jackson is and brings him home to meet everybody, who are all subsequently horrified that it isn't actually the singer.
Jackson does a great job of playing somebody who's imitating him, and it isn't just a small cameo. In sheer terms of celebrity, Michael Jackson was the biggest name to lend their voice to the show—and he was the biggest musical artist on the planet at the time.
4. Danny DeVito
When Danny DeVito dropped by to record his dialogue for The Simpsons, what he didn't know was that he'd be back a year later for a sequel. Such was the popularity of his character with the producers.
DeVito voices the character Herbert Powell, Homer's long-lost half-brother. When he's introduced, Powell is a wealthy car manufacturer—until Homer comes along and ruins it with his family vehicle idea.
Herb returned the next season and Homer helped him rebuild his fortune (although by season 24 he'd once again lost it).
The character was one of the most beloved by the fans, and his heartfelt forgiveness of Homer for ruining him was one of the show's first sweetest moments.
3. Dustin Hoffman
In season two, Lisa's teacher Miss Hoover was replaced for one episode by Mr. Bergstrom, voiced by the legendary Dustin Hoffman. (There's even a gag that references The Graduate as Mrs. Krabappel tries to seduce him while he resists her charm.)
Bergstrom's connection with Lisa is profound for her. She looks at a man with whom she identifies deeply, to whom she's more morally aligned than she is with her piggish father, Homer.
When Mr. Bergstrom inevitably leaves, Lisa catches him at the train station—and after an emotional goodbye, she's forced to go back to her family. Fortunately, Homer then proves why he's so good at being Lisa's dad by comforting her about his departure.
Dustin Hoffman's performance was incredibly moving and meaningful, and Lisa's journey throughout the episode is made more important by her friendship with Mr. Bergstrom.
2. Glenn Close
Homer sitting on top of his car and staring at the stars is one of the most tear-inducing moments in the history of The Simpsons.
His mother, who he thought was long dead, has just left him again in order to stay out of Mr. Burns' clutches—and this time, he got the chance to say goodbye to her.
Homer's actions towards his mother are antithetical to his actions towards his father: he's happy when she's around, and she mothers him sweetly. It all reminds the audience of something that Homer was cruelly denied in his youth.
Glenn Close's performance as Mona Simpson is a viscerally shattering one. Her presence gets us to see that Homer is pained by how he thought he was a horrible son and that no mother could want him.
Glenn Close returned to the role a few times afterwards, and she once again had the audience weeping at Mona's death.
1. Kelsey Grammer
There has never been a better guest star on The Simpsons than Kelsey Grammer. His role as the devious Sideshow Bob is legendary in its own right, and he has become one of the greatest TV villains of all time for his numerous attempts to murder Bart Simpson.
Sideshow Bob is cunning, funny, and tenacious in his personality. He's appeared on the show many times over the years, and almost always does so to attempt vengeance on Bart Simpson.
Kelsey Grammer's vocal performance is like a fine wine: smooth, charming, yet never more than one step away from malice. It's hard for us to pick the best episode that featured Sideshow Bob, but if we had to pick one, it'd be season five's "Cape Feare."