Scooby-Doo (voice of Frank Welker) and Shaggy (voice of Will Forte) are at a cinema with all of their favorite snacks, waiting for the movie to begin. Scoob says it's time they made a new movie and Shaggy agrees. We then go back in time to when Scooby met Shaggy when they were kids on a beach. Shaggy and Scooby go trick or treating and meet the rest of the gang — and stumble onto a haunted house.