Weekenders Adventures of Scooby-Doo is the another Weekenders/Scooby-Doo crossover made by Sonic876 and Frogadier55. It is a sequel to the Weekenders Adventures of Scooby-Doo! The Mystery Begins and Weekenders Adventures of Scooby-Doo Curse of the Lake Monster and appeared on Google Drive in May 13, 2017.
In a warehouse, the Mystery, Inc. gang illustrates a plan to catch the Luna Ghost who has kidnapped Daphne Blake (Sarah Michelle Gellar), flying around with her bound and gagged which goes astray but ends with Shaggy Rogers (Matthew Lillard) and Scooby-Doo (voiced by Neil Fanning) causing the Ghost to be caught. The gang unmasks the Luna Ghost, who is revealed the janitor of the Wow-O-Toy Factory, Old Man Smithers, who wanted revenge after Pamela Anderson refused to go out with him (it is implied that he kidnapped Daphne, mistaking her for Pamela). After solving the mystery, constant arguments among the members of Mystery Incorporated about Fred Jones (Freddie Prinze, Jr.) taking credit for Velma Dinkley's (Linda Cardellini) ideas and Daphne always getting kidnapped cause the gang to go their separate ways, much to the dismay of Shaggy and Scooby.
Two years later, Shaggy and Scooby are approached to solve the mystery of the popular horror resort Spooky Island, reuniting with Fred, Daphne and Velma, although none of the latter are thrilled to see each other, except for Shaggy and Scooby, who still want Mystery Incorporated to reunite. On the island, the gang meets Emile Mondavarious (Rowan Atkinson), the park's owner, who explains his theory that visitors are being cursed. Shaggy falls in love with a girl named Mary Jane (Isla Fisher), while Scooby is mysteriously targeted by demonic creatures. Velma meets a man named N'Goo Tuana and his henchman, the famous luchador Zarkos, who explains that demons once ruled the island.
The gang visits the island's abandoned ghost castle, where Daphne finds a pyramid-shaped artifact called the Daemon Ritus and Velma and Fred find a strange room with videos designed to address non-humans. When the gang returns to the hotel, they are attacked by the island demons, who kidnap numerous tourists including Fred, Velma and Mondavarious. The next day, Daphne is captured by Zarkos, while Shaggy and Scooby discover Fred, Velma and the tourists are now possessed by the demons. The two flee with Mary Jane until Scooby realizes she is possessed as well.
In the midst of an argument between Scooby and Shaggy, Scooby falls down a hole and is followed by Shaggy, who dives in to save him. Shaggy comes across a vat containing the protoplasmic souls of everyone who was captured, including the rest of the gang, and releases the gang's souls to their bodies. Velma discovers that the demons are destroyed in sunlight just like vampires, while Daphne and Fred's souls end up in the wrong bodies. Shaggy steals the Daemon Ritus and reunites with the gang except Scooby after their souls correct themselves.
Coming across Voodoo Maestro, the gang learns that if the leader of the demons absorbs a pure soul through the Daemon Ritus, then the demons shall rule the world for the next 10,000 years. The pure soul belongs to Scooby, while the demons' leader is revealed to be Mondavarious. Shaggy convinces the gang to put their differences aside and finally work together to save Scooby. They form a plan but it fails and Scooby's soul is extracted. Scooby is saved by Shaggy, wounding Mondavarious in the attempt.
Fred and Velma discover he is actually a robot, controlled by none other than Scooby's nephew, Scrappy-Doo (voiced by Scott Innes), who the gang abandoned years ago due to his egotism. Now vengeful, Scrappy transforms into a giant demon called Scrappy Rex (voiced by J. P. Manoux) to destroy the gang and rule the world using the tourists' souls he absorbed. Daphne fights Zarkos above the island's caves, knocking him through the roof, which exposes the demons to sunlight and kills them. Scrappy Rex picks up Scooby and taunts him but Scooby sticks his paws up his nose and gets stuck in his boogers until Scrappy flicks him out and sneezes on Scooby. Shaggy confronts Scrappy and rips the Daemon Ritus from his chest, freeing the souls and reverting Scrappy to his original self. Shaggy finds the real Mondavarious trapped in a hole and frees him. Scrappy and his minions are arrested.
Daphne and Fred kiss, Shaggy and Mary Jane hug along with Scooby, while Velma hugs a man she met earlier then playfully punches him in the chest while laughing. When Mystery Incorporated addresses the press, Velma thinks that Fred will take credit for her ideas again, however Fred lets Velma take the credit she deserves. Mystery Incorporated is then reunited while Scrappy-Doo and Zarkos are taken away. As Scrappy is arrested, he says "I would've gotten away with it, too! If not for you meddling sons of—", but the police shut the door of the helicopter before he can finish the sentence, while Daphne is talking to the press. As Scooby and the gang reconcile, the helicopter takes Scrappy and his minions away.
At the end, Scooby and Shaggy are seen at the Spooky Island Hotel eating hot peppers and screaming as smoke comes out of the hotel.
- Squire Flicker, Princess Flame, King Allfire, Queen Griddle, Sir Loungelot, Sir Blaze, Sir Burnevere, Sir Galahot, Sir Hotbreath, The Wandering Minstrel, Cinder and Clinker, Rocko, Heffer Wolfe, Filburt, Mal (Total Drama), Megan (LEGO Friends), Kyoko Kudo, Aya Kanazawa, Yuki Kashiwazaki, Ludo and The Dazzlings will guest star in this film.
- Mal (Total Drama), Megan (LEGO Friends), Kyoko Kudo, Aya Kanazawa, Yuki Kashiwazaki, Ludo and The Dazzlings will work with Scrappy Doo (Who in Disguise of Emile Mondavarious), Zarkos and N'Goo Tuana in this film.
- The storyline continues in Weekenders Adventures of Scooby-Doo 2: Monsters Unleashed.