From videos I've seen, none of the Simpsons actually speak, they just grunt a lot? Disappointing.
Is The Simpsons the only IP which does this?
Homer speaks.
EDIT: Speaking of grunting, I was playing as Marty McFly yesterday and it occurred to me that they had Parkinson's-addled Michael J. Fox in a recording booth taping jump and punch grunts, and the idea was all at once funny and weird to me.