Hank Azaria: We try to reward people for paying attention. If you don't pay attention it's a very funny show, but if you do pay attention there are lots of references to other things that are going on in our lives, in culture, in movies and so on.

Do you find your own character comes out in the parts you play?

Nancy Cartwright: We all have a little Bart inside of all of us, Bart gets away with doing the things we all wish we could get away with. Playing Nelson gives me the opportunity to be Bart's nemesis, he allows me to be this angry guy, tough and a bully. It's great fun as an actor to wrap my wits around that. Ralph Wiggum, he's a sweet innocent guy! It doesn't matter what he says, I play it and I know everyone will respond a certain way.

Harry Shearer: I play both Burns and Smithers, the main thing it draws out in me is my own deep self love! All the characters I play have a common corrupt venality - I have a well of that to draw on!

Hank Azaria: Although I play Moe, Apu, Wiggum, Professor Frink, oddly I feel like Lisa Simpson inside. I've been doing silly voices since I was a child - it's a nice outlet for that.