Nancy Cartwright is historic for her Bart Simpson voice. We were doing
a cartoon show a few years ago, and during some downtime, I heard some
commotion and it was Nancy with a little man in her mouth screaming
to get out. Here’s how it’s done. Puff your cheeks out and
talk, leave your lips loose, and closed, so that a very little air may
escape out of your mouth. You won’t be able to pronounce ‘m’
or ‘b,’ but who needs them anyway? Say something like, “let
me out of here!” You’ll be surprised at how easy it is to
speak and how great and weird it sounds.
The real trick is to act like you’re surprised or a bit embarrassed
that it’s happening. This is a great trick for sounding like you’ve
been gagged, or stuffed in a wise guy’s trunk.