Frank Welker, who's been voicing ascot-sporting Fred since 1969 and Scooby-Doo since 2002, will return to voice the classic characters.
No one has been announced to voice ditzy Daphne. Grey Griffin (aka Grey DeLisle) has been voicing her since 2000.
Tracy Morgan will play Captain Caveman, who's appeared in other Hanna Barbera cartoons, but not the original "Scooby-Doo." The premise of the movie: The Scooby Gang join forces with other Hanna-Barbera characters to save the world from Dick Dastardly.
Over the years, the Mystery Inc. crew has had crossovers with everyone from Batman and Robin to the Harlem Globetrotters.
"Scooby" is set for a May 2020 release.