Charlie's motivations for returning to Earth in All Dogs Go to Heaven seem kind of murky. He's clearly enticed by the finer things in life (after all, he agrees to leave his partnership with Carface and abandon his life and friends for a good chunk of the business profits), so you'd think heaven would be, well, heaven. Going back to Earth just to get revenge seems not just petty but kind of silly when everything Charlie is motivated by in life (food and prosperity) is provided for him in heaven.
It would have been one thing if Charlie had some unfinished business on Earth, if he had a family to take care of, or if he didn't want to leave a girlfriend behind. But Charlie doesn't really have much going for him on Earth. He's broke, his best friend killed him, and — let's face it — he can't have that many years left of his life considering that, according to the American Kennel Club, the average lifespan of a German Shepherd like Charlie is just seven to ten years.
