It has been on air since 1989 - but some fans of The Simpsons are only just learning why creators changed a key detail about one of its characters. When making his first appearance in episode three of the first season, Homer's Odyssey, Waylon Smithers, who works as Mr Burns' personal assistant at the Springfield Nuclear Power Plant, has black skin. However, in later episodes, his skin colour changes to yellow, making fans wonder why the creators decided to change his race. While some people