Scooby-Doo on Zombie Island sequences of interplay between Shaggy and Scooby for him. After Don Messick's death, Scott Innes replaced Messick as the voice of Scooby-Doo. Casey Kasem did not reprise his role as Shaggy Rogers as he wished to only voice Shaggy if the character became a vegetarian, like himself. Instead, Billy West provided the voice for Shaggy. Mary Kay Bergman was cast as Daphne when the character was taken in a new direction. B.J. Ward, who played Velma in the "Johnny Bravo" crossover episode, reprised her role in this film. Frank Welker is the only actor from the original series to reprise
Scooby-Doo and Scrappy-Doo (1979 TV series) threatening cancellation for the show, whose ratings were in decline. ABC was going to choose between two shows-Scooby-Doo or an unnamed pilot from Ruby Spears Enterprises. Therefore, for its 1979–1980 season, "Scooby-Doo" was given a major overhaul, adding the character of Scooby's nephew Scrappy-Doo, voiced by Lennie Weinrib, and changing the name of the show to "Scooby-Doo and Scrappy-Doo". Although still present in these episodes, the characters of Fred, Daphne, and Velma became less essential to the plot and Shaggy, Scooby and Scrappy were the main focus. Marla Frumkin took over Pat Stevens' role as Velma Dinkley towards the end