Frank Welker Fred, Scooby Voice Mindy Cohn Velma Voice Grey DeLisle Daphne Voice Matthew Lillard Shaggy Voice John Billingsley Dr. Henklefust Guest Voice Lewis Black Mr. E Guest Voice Linda Cardellini Marcy "Hot Dog Water" Fleach Guest Voice Vivica A. Fox Cassidy Williams Guest Voice Mark Hamill Crybaby Clown Guest Voice Kate Higgins Mayor Janet Nettles Guest Voice Matt Lanter Baylor Hotner Guest Voice Jim Rash J.R. Kipple Guest Voice Roz Ryan Gorgeous G Guest Voice Sam Register Executive Producer Spike Brandt Producer Tony Cervone Producer Michael Ryan Writer