Trivia: You can see Matt Groening laughing at Itchy & Scratchy in the audience of the Annual Cartoon Awards.
Trivia: In "The Bob Next Door", Marge comments that a lot of people sound like Sideshow Bob, including Frasier from "Cheers" and "Frasier", and Lt. Cmdr. Tom Dodge in Down Periscope. Those are both characters played by Kelsey Grammer, who voices Bob.
Trivia: Most of the main cast of 'Cheers' has been on the Simpsons, including Kelsey Grammer as Bart's returning nemesis, Sideshow Bob. When Homer is kicked out of Moe's Tavern, he looks for a new bar and ends up in Cheers, where the other Cheers cast members voice their old characters. However, Grammer's character of Frasier does not speak.
Trivia: In this episode, Bart attends a Spinal Tap concert. Harry Shearer, who voices a number of characters on the show, played Tap bassist Derek Smalls in the film "This Is Spinal Tap."
Trivia: In this episode Donald Sutherland plays the museum curator. In the 1975 film "The Day of the Locust" he plays a character called "Homer Simpson".
Marge vs. the Monorail - S4-E12
Trivia: The entire premise of this episode, where a man in turn-of-the-century garb sings and charms his way into the townspeople's hearts as part of an elaborate con, is a takeoff of the musical, "The Music Man" (1962). Even the tunes of the songs they sing are similar.
Homer's Barbershop Quartet - S5-E1
Trivia: During the episode, Skinner reveals that his POW number was 24601. This is the same as Sideshow Bob's inmate number and takes after the prisoner number of Jean Valjean in Les Misérables. That same prisoner number was also Hank Jennings' in "Twin Peaks".
Trivia: Near the beginning of the episode, Lisa looks at a book and says that Santa's Little Helper was fixed. The book is an actual book that tells about Simpsons episodes, entitled "The Simpsons: A Complete Guide to Our Favorite Family."
Trivia: When Fat Tony and his gang are outside of the Simpson house, he says "Tonight, I want you boys to take out the Castellaneta family". Dan Castellaneta provides the voice of Homer on the show.
Itchy and Scratchy: The Movie - S4-E6
Trivia: Lisa refers to Dustin Hoffman and Michael Jackson voicing guest characters in the "Itchy & Scratchy" movie. She says "They didn't use their real names, but you could tell it was them." This is a sly reference to Hoffman and Jackson's pseudonymous appearances in The Simpsons, in Seasons 2 and 4, respectively.
Trivia: When homer lights his high school diploma on fire and starts singing the "I am so smart" song, when homer misspells smart, that was an actual mistake by Dan Castellaneta, who spelled it s-m-r-t instead of s-m-a-r-t, and then corrected himself.
Last Exit to Springfield - S4-E17
Trivia: Mr Burns' reaction - right down to his animation - to the singing of the Union towards the end is a direct spoof of the Grinch (from The Grinch Who Stole Christmas) by Dr. Seuss. His characters also spoke in rhyme, which is why some of Mr Burns' lines are nonsense.
Trivia: Hank Azaria, voice for many of the characters on the Simpsons, said in an interview with Conan O'Brien that most of his voices were just bad celebrity impressions. Moe Syzlak is Al Pacino, Louie the cop is Sylvester Stalone, and Comic Book Guy is someone he went to college with who had a personality much like comic book guys. With other characters who Azaria doesn't do are also celebrity impressions. For example, Mayor Quimby is JFK.
Trivia: When Homer says to Lisa "How could they change my character from cool to stupid?" and Lisa replies "creators love to tinker with shows, they drop characters, change some and push others into the background", in the background walking past the window you can see Mr. Largo and The Capitol City Goofball: two long since backgrounded characters.
I Love Lisa - S4-E15
Trivia: Ralph Wiggum was named after Ralph Kramden on "The Honeymooners" because the character was intended to be a loudmouthed smaller version of Homer. He wasn't established as Chief Wiggum's son until "I Love Lisa."
Lisa's Pony - S3-E8
Trivia: At King Toot's music store, Homer is asked whether Lisa's Sax is a tenor or an alto. Actually, it's a baritone.
The Old Man and the Lisa - S8-E21
Trivia: Guest star Bret Hart is missing the four hearts that are usually on his right thigh.
Answer: Willy referred to an encounter he believed he had with actual aliens, while Wiggum thought he was referring to the arcade game.