T-Bone, Heather, and Corky are three major characters in the All Dogs Go to Heaven: The Series episode "Charlie's Angle." They are three angel puppies to be trained, and they are are assigned to Charlie by Annabelle and Chief in order to teach him responsibility. Instead of teaching them to help others, he uses them to serve him whatever he wants.
Because he doesn't teach them the right things, they mess up when he needs help. Thus, when they are forced into the HeelBoy 2000 by the brainwashed dogs, they apologize to Charlie for messing up, but he tells them it isn't their fault, so they are brainwashed and turned evil.
When "Carface" and "Killer," who are "operating" a machine that "turns anyone who gets inside into monsters," turn out to be Chief and Annabelle, respectively, and the three angels-in-training turned out to have actually been trained guardian angels all along, Chief and Annabelle decide to put the three angels-in-training in charge of Charlie to make sure he learns his lesson. Instead, however, Charlie decides he'd rather be nasty, so he goes inside the machine, which Annabelle "operates."
T-Bone, Heather, and Corky are voiced by Shaun Fleming, Anndi McAfee, and Alan Roberts, respectively.