Mystery Inc. travels to San De Pedro,
California for the "Mega Mondo Pop! Comic ConApalooza" so
Shaggy Rogers and
Scooby-Doo can enter a costume contest as their favorite superheroes, the Blue Falcon and
Dynomutt. There, they meet Jennifer Severin, a film producer in the midst of making a dark and gritty
Blue Falcon film; its leading actor Brad Adams; Hank Prince, the owner of a comic book store that Shaggy frequently visits; his nephew Austin; Owen Garrison, the washed-up star of the original
Blue Falcon television series; and Jack Rabble, a former BattleBots champion. When Shaggy and Scooby try to get Garrison's autograph, he instead rants to them about how Severin's studio intends to remove all traces of his series in preparation for the film. Amidst a screening for its trailer, Mr. Hyde, an antagonist from the
Blue Falcon television series, emerges to terrorize the conventioneers. As Mystery Inc. offers to investigate, most of them consider Garrison to be the culprit, but Shaggy and Scooby refuse to believe them. Using surveillance footage, they discover that Severin stands to gain increased publicity for her film from the incident while Adams dislikes his role in it and is hoping for an opportunity to resign. Realizing Hyde's attacks were based on episodes of the
Blue Falcon television series and that his next attack will involve a
mutagenic ooze capable of transforming living creatures into monsters, Shaggy and Scooby later enter a storage room, where they stumble upon Hyde's lair before he chases them out and attacks the city with a harmless placebo of the ooze. Having been humiliated during the attack, San De Pedro's
mayor, Ron Starlin, closes the investigation, relinquishes Mystery Inc.'s services and revokes their access to the convention. Upon learning the
Blue Falcon film premiere is being held at the local
ballpark and deducing it will be Hyde's next target, Fred, Velma and Daphne enlist Austin and Rabble's help in sneaking past the convention's security so they can infiltrate Hyde's lair. There, they learn that the villain has been spying on the convention and ballpark before witnessing a giant Hyde rampaging in the latter. Meanwhile, Shaggy and Scooby find themselves trapped in there while searching for something to eat. Seeing Austin in danger, the duo rescue him before their friends arrive to defeat the giant Hyde and discover that it was actually a mech seemingly piloted by Garrison. Despite his claims about someone knocking him out to
frame him for the attack, Garrison is nearly arrested. However, Shaggy and Scooby witness the real Hyde having
carjacked an
armored car. Scooby foils the robbery, only for Hyde to gain the upper hand. Nonetheless, Garrison, taking on his former Blue Falcon role, joins Scooby in defeating the villain. Hyde is then revealed to be Rabble, who had been plotting to take revenge on the convention after he was ousted from BattleBots due to weaponizing one of his robots with live
missiles, forcing him to make money off of his appearances there ever since. After forcing the premiere to be held at the ballpark and planting Garrison in the remote-controlled mech, he would use the attack to divert the armored car into a
detour to carjack it and make off with the five million dollars' worth of the convention's entrance fees it had. As Rabble is apprehended for his crimes, Starlin arrives to congratulate Mystery Inc. for their work and apologize for misjudging them. Some time later, an impressed Severin produces a sequel to her
Blue Falcon film, with Garrison guest-starring as the father of Adams' character and Scooby portraying Dynomutt. == Voice cast ==