All-Star Cast: According to the voice actors themselves, subverted, as they say they're 'the most famous people never recognized'.
Cross-Dressing Voices: Brought up between several voice actors. Nancy Cartwright says she doesn't like doing Bart Simpson live because people would be weirded out that Bart Simpson is voiced by a woman. During the end credits role call, Charlie Adler speaks like Cow from Cow and Chicken.
Method Acting: A story is told of how Mel Blanc was in a coma after a car crash, and the doctors managed to wake him back up by addressing him as his various voices, which he would respond in character. James Arnold Taylor also talked about how you can't just have a funny voice, but be capable of doing everything in that voice, like singing, getting punched, and doing an impression of the character doing an impression.