Has anyone else noticed this, this is something that just now occured to me...
Anytime the show does a flash-forward sequence, and we see the gang either as teenagers in high school/college, or all grownup, Buster's the only one who goes through a voice change? Arthur, D.W., Francine, Muffy, Binky, Brain, etc, all their voices still sound exactly the same older as they did when they were eight, but Buster somehow is a different story.
Actually, I take that back, whenever they do sequences where they're really old senior citizens, they at least do fake stereotypical old people voices.