She [Julie Kavner] rarely performs Marge’s [Marge Simpson’s] voice in public because she believes it “destroys the illusion. People feel these are real people.”
My two cents
That’s garbage, especially when the other voice actors have no problem performing their voiceovers in public. I’ve never heard a fan (or a critic) walk away disillusioned just because they saw a voice actor doing their work in the flesh; it’s a faulty premise to have things driven by the assumed feelings of viewers. If a survey was done showing that 99 per cent of viewers believe that the Simpsons characters are just cartoon characters (instead of real people), does that mean she would then do it? I doubt it.
Wikipedia. (2011). Julie Kavner. Available: http://en.wikipedia.org/wiki/Julie_Kavner. Last accessed 22nd Feb 2011.