As you probably know, veteran DJ and voice artist Casey Kasem originated the role of Shaggy in the first series, Scooby-Doo Where Are You!, back in 1969. Kasem played the role in all of the show's various incarnations and appearances for almost three decades.
At some point, Kasem became a vegetarian and asked that ever-hungry Shaggy become one as well. The studio didn't want to do it so, when Kasem was reportedly asked to perform the role for a Burger King commercial in the 1990s, he refused.
Billy West (Futurama) took over and played Shaggy in the direct-to-video movie Scooby-Doo on Zombie Island. Scott Innes took over the