From Mental Floss.
Mr. Burns, Homer’s boss, is the richest man in Springfield (or the world). Mr. Burns was based on Olav Thon, a Norwegian businessman who reputedly took over a couple of businesses in his town and shut them down. Also, Frederick Olsen, a reclusive millionaire, who owned several companies, including Timex, is mentioned as a Mr. Burns influence. And Matt Groening’s high school teacher, Mr. Bailey.
The original breakout star of the series, Bart’s name is an anagram of the word “brat.” Bart’s character was based on another very mischievous cartoon character, Dennis the Menace. Creator Matt Groening said he was “always disappointed” that the Dennis the Menace TV show character wasn’t as mischievous as the comic strip.
Gumble is Homer’s best pal and the town drunk. Barney was based on a character from The Jackie Gleason Show of the 1960s called Crazy Guggenheim (played by actor Frankie Fontaine). Crazy Guggenheim was a rum-soaked drunken character who would chat with Jackie in comedy skits. Jackie played the bartender, the straight man to Crazy.
PROFESSOR JOHN FRINK
Springfield’s resident mad scientist was originally scripted to be an evil scientist. But during his first reading of the character, actor Hank Azaria ad-libbed his impression of Jerry Lewis’ character in The Nutty Professor. Everyone loved Hank’s interpretation and his Nutty Professor slant on Frink stuck. (Jerry Lewis later guest starred on a Simpsons episode, playing Professor Frink’s father.)
Apu runs Springfield’s local Kwik-E Mart. This very ethnic character was based on Peter Seller’s character in one of his best films, The Party.
OTTO THE BUS DRIVER
Otto Mann was based on Guns ‘n’ Roses guitarist Slash. Both Otto and Slash have long black curly hair and both collect snakes.
KRUSTY THE CLOWN
Krusty the clown is Springfield’s TV star, a blasé, shlocky, Catskills-based comic. Krusty was based on a real-life clown named Rusty Nails, a semi-funny, semi-scary clown Matt Groening used to watch as a child. Krusty’s biography on the show was based on comedian Jackie Mason, a world-weary Jewish comedian whose father was an Orthodox rabbi.
The quintessential cheesy, grade B movie actor, Troy McClure is actually a combination of two grade B movie stars: Troy Donahue and Doug McClure. In real life, Doug McClure was not offended by the character, but flattered instead. His daughter often called him “Troy.”
MOE THE BARTENDER
Moe Szyslak, the very cranky local bartender and one of Homer’s trusted pals. Moe was based on the voice of acting great Al Pacino (Moe’s favorite film is The Godfather.) and possibly comedian Rich Hall, a friend of many Simpsons writers.
See the rest here.