Behind the 100 voices chattering away in The Simpsons are a cast of 12 talented, versatile voice actors. Here's how those voices break down, according to @Jishai.
Castellaneta, Azaria, and Shearer voice the most characters, together accounting for roughly 60 percent of the voices on the show.
Another cartoon known for its versatile voice artists is South Park, whose entire cast of raucous characters are mostly voiced by four actors, including creators Trey Parker and Matt Stone.
Versatility is a skill common to most successful voiceover actors. Many of them create and perform several, if not dozens, of cartoons and puppets throughout their careers — often in the same series. For example, Mel Blanc — known as the Man of a Thousand Voices — performed many beloved characters from the Golden Age of American Animation, including Bugs Bunny, Daffy Duck, Sylvester the Cat, Barney Rubble, Mr. Spacely, and Woody Woodpecker.