Weekenders, Billy, and Mandy's Big Boogey Adventure is another Weekenders/Cartoon Network crossover film made by Sonic876. It will appear on Google Drive in the near future.
Grim is sued for dereliction of duty by his old rival, the Boogey Man, the former having failed to reap General Skarr thanks to an intervention from Billy and Mandy. Grim and the children (including Irwin) are set to be exiled by the Underworld Court and placed in the custody of Boogey, with Grim being stripped of his job and powers. Numbuh 3 of the Kids Next Door is the court-appointed Grim Reaper. Boogey reveals his plan is to steal Horror's Hand, an artifact capable of bringing people's deepest fears to life and transforming anyone who conquers their fear into the scariest and most powerful being in existence; Boogey himself believes that with its power, children will fear him again. The group eventually escapes and plans to obtain the hand for themselves for various reasons (Grim believes it will get him his job back, Mandy sees it as the way to conquer the world, Irwin thinks it will help him win Mandy's heart and Billy just wants to use it to get a candy bar).
Both groups eventually reach where the hand is held, where they meet Horror the Ancient (George Segal), a living statue that cut off the hand -originally his left hand- having placed his fears within it. To obtain the hand, two rivaling groups must embark on a race across the Cannibal Run - the most dangerous section of the River Styx - as well as facing their worst fears. Grim and the children win and scrape to obtain the hand. Billy, Irwin and Mandy are easily subdued by their worst nightmares in turn (a spider-clown-mailman hybrid, telling jokes to wild bears and growing up into an optimistic woman married to Irwin, respectively), leaving Grim to claim the hand unaffected, revealing he lived his worst nightmare everyday - living with Billy and Mandy. The hand however is almost immediately stolen by Boogey (who uses it to scare Grim to pieces, though Grim actually blew himself up on purpose). Believing he has won, Boogey turns out to be incapable of facing his worst fear, realizing that he is not at all scary. He suffersamnesia after a series of accidents, and ends up afraid of everything. Grim is reinstated as the Grim Reaper, partly because Numbuh 3 was too much of an airhead to actually reap anyone. In the end, a naked, cut up Billy from two weeks in the future appears before them to warn that if Mandy had used Horror's Hand, she would have taken over the world in two weeks, becoming the Lord of Horror from his time. Grim decides to put the hand in his trunk to ensure that that future never comes to pass. Future Billy eventually goes back to the future to make sure that things were set right. The credits roll, showing the aftermath for each character.
The epilogue shows how Billy went back to the future, and finds that Fred Fredburger obtained Horror's Hand from Grim's magic trunk and took over the world as the new Lord of Horror.
- Pippi Longstocking, Bibi Blocksberg, Kurumi Tokisaki, and The Dazzlings guest stars in this film.