The Simpsons has been holding a lot of records. One of them being the longest primetime cartoon show that has been 'The Flintstones' and 'Bonanza'. The even hold a world record for having the guest celebrity voices on the show. Some voicing themselves or another character. Here are a few that are still memorable or voicing the character today.
Danny DeVito- Danny DeVito, known for his shows like TAXI and It's always sunny in Philadelphia voice Homer's half-brother in the second season and third season of the show. I think he also voiced himself in another later Simpson episode. What has happened to Homer's brother? Well Danny DeVito couldn't be around the show since his schedule was busy. They decided to let him voice again only his brother was poor again. You have to watch the episodes to find out how he got rich.
Joe Mantegna- Voices Fat Tony and 'Fit'-Fat Tony. Started voicing the supposed mob boss around the third season and let's just say...he hasn't stop. Even though he is acting in shows like Criminal Minds and it's spin off shows, he still likes to voice a criminal mobster that has been in almost every season of the Simpsons. I guess this is a plus for him after staring in the horrible Godfather part III movie. His character Fat Tony (Fit-Fat as well) is supposed to be a character like in the godfather, or any of those mob bosses of the time.
Mel Brooks- Appearing as himself in one episode, Mel Brooks is known for many things. A Director, Producer, Actor...but what is he doing in Springfield? It seems Homer lost his license and long story-short, he has to ride a limousine. One of his passengers is Mel Brooks. He makes this cameo memorable. I don't know if he's been in many recent episodes.
David Duchovny and Gillian Anderson- Also known as Mulder and Scully to X-Files fans, when that show was becoming popular, one of the writers decided to mix the two shows together. David and Gillian portray their characters on X-Files helping them solve an alien mystery Homer saw after getting drunk. Let's just say...it's a pretty good episode. Sadly, I never got into X-Files, but this episode was worth their cameos.
Kathleen Turner- Playing an icon of a doll similar to Barbie, Kathleen Turner voices the woman who created 'Malibu Stacy'. During the era of the 'Talking Barbie doll', the episode started to make a talking 'Malibu Stacy' as well. It's not a doll Lisa Simpson would like as she decides to go to the inventor of the doll only to find out she no longer works with the company. Kathleen Turner does a pretty good job only voicing one time.
John Waters- John Waters is a director of raunchy films, but what is he doing in Springfield? He voices a character named John who's just as flamboyant as the real actor is. Homer....doesn't take it well finding out John is gay. This episode is pretty deep explaining Homer's gay phobia eventually accepting John for who he is. This episode was tough to create back in the 90's and would be taboo then, now...it's one of the best episodes of the Simpsons.
Kelsey Grammer- Ever since the first season of the Simpsons, Sideshow Bob was voiced by Kelsey Grammer. He used to be Krusty's former sidekick until he framed Krusty. Ever since then, Kelsey Grammer has been heard in almost every season when Sideshow Bob appears. Always wanting to kill Bart Simpson and harm the Simpson family. Most of the seasons, something happens to Sideshow Bob. He gets married, dies, plots revenges, becomes mayor of Italy and so on and so forth. I don't think Kelsey Grammer, or Sideshow Bob will leave Springfield anytime soon.
David Hyde Pierce- Around the eighth season of the Simpsons, the show decided to poke fun at a certain show named 'Fraiser'. Kelsey Grammer voiced Sideshow Bob, so they decided to throw in David Hyde Pierce who portrays Sideshow Bob's brother Cecil. He too plots revenge with world domination and killing Bart. They even poked fun on the episode since both Kelsey and David play brothers on Fraiser.
Johnny Cash- During Homer's 'trip', he visions a coyote voiced by Johnny Cash. Giving Homer words of wisdom and helping him out of his journey. After Homer fights with Marge, he ends up stranded at a golf resort having a drug trip after eating an insanity paper during a chili cookoff. He soon sees the coyote and the late Johnny Cash voiced him.
Phil Hartman- This story is pretty tragic, but there once were two characters named Lionel Hutz and Troy McClure and they both were voiced by Phil Hartman. He was a great actor starring in shows like SNL, News Radio and many more. He even voiced other characters in other shows, but he shined voicing on the Simpsons. Sadly...he was killed by his wife who took her own life afterwards. Sadly, the characters that he voiced were silenced forever. We still see them in backgrounds, but they are no longer voiced by Hartman. We miss him.
Patrick Stewart- Homer joined a secret club around the sixth season. The leader was voiced by Patrick Stewart. Let's just say.... Homer's stay was short lived, but Patrick didn't just voice him. He voiced another character in later seasons who worked at the Nuclear Power Plant. Actually, covering Homer's mistakes and was retiring. It seems any character Patick voices has to find a way to save Homer's ass.
Glenn Close- In season seven a mystery was answered about whatever happened to Homer's mother. She is revealed and is voiced by Glenn Close. She explains her vanishment in a few episodes and sadly, her character dies. Glenn Close still voices Homer deceased mother in his dreams and everything else that has happened to him. I felt bad for Homer. Losing a mother can be heartbreaking. Glenn Close does a perfect job voicing Homer's mother dead or alive.
Penny Marshall- Considered one of the first guest stars to voice on the Simpsons (I don't think that's right though) Penny Marshall portrays a babysitter who's really a bandit. Bart and Lisa have to deal with her but are saved by Maggie and take care of the babysitter bandit themselves. Penny Marshall was considered one of the first to guest voice on the show, but there could have been others before. I don't know. She's no longer with us and the babysitter bandit was a one-time character.
Jane Kaczmarek- Around later seasons, the show added new characters to see how long they would last. One of them was a female judge voiced by Malcom in the middle mom Jane Kaczmarek. The characters have similarities to the mother in Malcom. She's tough and forces Homer and Bart to be lashed together to teach Homer he's a bad parent. Marge is soon roped into the 'bad parent' trope as well. The character is still seen and is still voice by her.
Meryl Streep- During the sixth season of the show.... a famous guest star voiced the Reverand's daughter named Jessica. She is worse than Bart would be going as far as to steal money from the collection plate and have Bart face the consequences. Meryl does a good job making a poor innocent sweet Reverand's Daughter so evil. Not many people knew it was her at the time, but well.... hearing the daughter now.... I know it's her voice. She hasn't voiced the character since.
Bryan Cranston- In a later season, Bryan Cranston voices a James Bond like character that only Homer can see. He gives Homer some advice on how to better his marriage with Marge. Only he can see him, and others wonder if Homer is ok. He eventually tries to make his wife happier with suggestions that Bryan Cranston's character gives him. I guess it seems to work. I vaguely remember the episode. Bryan Cranston also starred in a couch gag portraying himself as Walter White.
Winona Ryder- Lisa always tries to be the best in everything. However, she has to prove herself when another girl (voiced by Winona Ryder) comes into the school. She is better at Lisa in everything. Making Lisa jealous enough to sabotage her project. Eventually, she feels bad and reveals that she did it. However....Ralph Wiggum wins beating Lisa and the new girl. Winona Ryder sadly never voices the character again. The girl's name is Alison.
Elisabeth Moss- Having a short cameo on the Simpsons, Elisabeth Moss plays a young woman who is pregnant, and Homer delivers her child. Homer has a special bond with the child and Elisabeth Moss' character is ok with that. Until... the father comes home. Homer is told never to see the baby again after Marger finds out the secret. Homer feels upset about what happened and well.... his baby Maggie forgives him. Short, but sweet, Elisabeth does a good job.
Ray Romano- During the final season of 'Everybody Loves Raymond', Ray Romano voices a roofer that only Homer can see. He eventually ends up in a loony bin only for Ray's character, who is named Ray, to appear. The first time this episode was on air, Ray Romano hints to Homer about the show 'Everybody Loves Ray' to him. Ray Romano's ok, but I think he also was a one-time character since he hasn't been seen since.
Albert Brooks- In my opinion, Albert Brooks (or A. Brooks as he's known) was considered the first guest star to voice on the show. He's voiced a lot of characters on the show. Even voiced the main villain in the movie the Simpsons had back in 2007. He voiced Hank Scorpio, who was a super villain, but is seen once and only once. He voiced Jaque a bowling instructor that lusted for Marge. He voiced that character again in later seasons. Albert Brooks voices many characters, and I don't think he's going to stop anytime soon.
If I listed anymore characters on the show, it would be a long list. Almost every Beatles (minus John) guest voiced as themselves. Lady Gaga, Barry White, Ludacris, Dolly Parton. Any famous singer, sports star, even SNL stars have guest voiced as either another character or themselves in almost every season. Recently they did an episode with Lizzo guest voicing as an elf. Richard Gere voiced himself when Lisa was becoming a Buddhist. Let's just say.... look on-line and you'll be amazed of the list of people guest voiced on the Simpsons as themselves or another character.