Billy (voiced by Tress MacNeille) is Troy McClure's assistant who appeared in "Lisa the Simpson", "Bart the Mother" and "The Boy Who Knew Too Much". He was supposed to appear in more episodes but due to McClure's voice actor Phil Hartman's untimely death he was retired along with McClure. He is a child who appears in Troy McClure's educational films. His movies include "Birds: Our Fine Feathered Colleagues", and "In The Kitchen with DNA". A similar boy, Jimmy, appeared in "Lisa the Vegetarian."