Suggestions by @luisperezcozar

George Newbern

as Superman in Scooby-Doo! & Justice League Unlimited

Phil LaMarr

as Green Lantern/John Stewart in Scooby-Doo! & Justice League Unlimited

Susan Eisenberg

as Wonder Woman in Scooby-Doo! & Justice League Unlimited

Kate Micucci

as Velma Dinkley in Scooby-Doo! & Justice League Unlimited

Grey DeLisle

as Daphne Blake in Scooby-Doo! & Justice League Unlimited

Frank Welker

as Fred Jones in Scooby-Doo! & Justice League Unlimited

Matthew Lillard

as Shaggy Rogers in Scooby-Doo! & Justice League Unlimited

Frank Welker

as Scooby-Doo! in Scooby-Doo! & Justice League Unlimited

Sam Liu

as Director in Scooby-Doo! & Justice League Unlimited