Billy & Mandy's Big Boogey Adventure
DVD cover
Created by	Maxwell Atoms
Written by	Nina Bargiel Jeremy Bargiel Maxwell Atoms
Story by	Maxwell Atoms
Directed by	Shaun Cashman Kris Sherwood Gordon Kent Matt Engstrom Eddy Houchins Sue Perrotto Robert Alvarez Russell Calabrese Phil Cummings Mike Lyman Christine Kolosov
Voices of	Greg Eagles Richard Horvitz Grey DeLisle Vanessa Marshall Fred Willard George Segal
Composers	Gregory Hinde Drew Neumann
Country of origin	United States
Original language	English
Production
Executive producer	Maxwell Atoms
Producer	Louis J. Cuck
Editor	Illya Owens
Running time	80 minutes
Production company	Cartoon Network Studios
Original release
Network	Cartoon Network
Release	March 30, 2007 (2007-03-30)

Billy & Mandy's Big Boogey Adventure is a 2007 made-for-television animated adventure fantasy comedy film produced by Cartoon Network Studios, and is the first made-for-television film based on the animated series The Grim Adventures of Billy & Mandy, the second being Billy & Mandy: Wrath of the Spider Queen. Big Boogey Adventure premiered in the United States on March 30, 2007, and in the UK on February 14, 2007, and was released on DVD in the U.S. on April 3, 2007.

The events of the film take place during the sixth and final season of The Grim Adventures of Billy & Mandy.

In the future (in about two weeks), in a dystopian Endsville, an evil being known as the "Lord of Horror" orders robotic duplicates, Billybot and Mandroid, to go back in time to eliminate Billy and Mandy and prevent them from reaching a powerful hand-like artifact in the Lord of Horror's possession before his past self does. Billy and Irwin of this time hope their past selves can stop the Lord of Horror's evil plans.

Two weeks prior, Grim is sued for dereliction of duty and misuse of his abilities by his old rival, the Boogey Man, the former having failed to reap General Skarr (who had accidentally created a hole in his chest) thanks to an intervention from Billy and Mandy. Grim and the children 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 and Numbuh 3 from Codename: Kids Next Door becoming his court-appointed replacement. Boogey reveals it was part of his plan 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 once again. The group eventually escapes and plans to obtain the hand for themselves for various reasons.

Both groups eventually reach where the hand is held, where they meet Horror the Ancient, a living statue and source of the Hand, having channeled his fears within it and cutting it off in an attempt to make himself brave. To obtain the hand, the 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 respective worst nightmares, leaving Grim to claim the hand unaffected, revealing he goes through his worst nightmare every day — being forced to live with Billy and Mandy. The hand however is almost immediately stolen by Boogey who uses it to scare Grim so badly that he explodes. Believing he has won, Boogey is shocked when Grim promptly reforms himself and laughs at Boogey for thinking he was capable of scaring him. Boogey realizes the hand is making his worst fear a reality, forcing him to confront the truth that he is not scary; he subsequently suffers a series of humiliating accidents where everyone there hysterically laughs at him. After which Grim reveals he had actually turned the hand's power off right after he picked it up, meaning Boogey wasn't ever scary at all. Mistaking Fred Fredburger's comments about nachos for actual philosophical advice, Billy has an epiphany that he and his friends obtained what they wanted without the need for Horror's Hand.

After the Underworld Court arrive to finish Boogey's business of banishing Grim forever, Mandy makes them reinstate Grim as the Grim Reaper because he saved the world from a future ruled by Boogey, but also because Numbuh 3 was too much of an optimist to actually reap anyone in the court's view. In the end, Billy from 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. Subsequently, Boogey is discovered to have become afraid of everything having suffered "a few too many hits on the noggin" during his humliation. Future Billy eventually goes back to the future to make sure that things were set right.

The credits show what each character did after the events of the film, such as General Skarr using the hole in his chest to keep birds, Mandy becoming the new captain of Boogey's ship, Numbuh 3 starting her own Reaper-for-hire service (which results the people laughing at her), Dracula stealing Grim's scythe for use as a golf club, Irwin being bedridden for getting infected with mono and cooties after kissing Mandy, Billy eventually becoming President of the United States and Boogey living in fear ever since his defeat.

The epilogue shows how Billy went back to the future to find that it has not changed as Fred Fredburger has obtained Horror's Hand from Grim's magic trunk and took over the world as the new Lord of Horror, having conquered his fear of running out of nachos.

• Grey DeLisle - Mandy / Mandroid / Older Mandy / Milkshakes / Some Kid
• Greg Eagles - Grim / Sperg / Pirate #6
• Richard Steven Horvitz - Billy / Billybot / Harold / Pale Ghoulish Juror / Chippy the Squirrel / Future Billy
• Vanessa Marshall - Irwin / Pirate #5 / Unicorn / Future Irwin
• Maxwell Atoms - I'll Cut You Guy / Pirate #2 / Horrorbot / Burnt Skeleton Guard
• George Ball - Peequay
• Jane Carr - Bride of Frankenstein
• Greg Ellis - Creeper / Horror's Hand / Pirate #3 / Paperboy
• Bart Flynn - Giant Cyclops / Ugly Pirate
• C. H. Greenblatt - Fred Fredburger / Pirate #4
• Jennifer Hale - Gladys
• Dorian Harewood - Older Irwin
• Phil LaMarr - Space Villain / Glacier of Evil / Dracula / Judge Roy Spleen / Underworld Cop
• Rachael MacFarlane - Two-Headed Parrot
• George Segal - Horror
• Armin Shimerman - General Skarr / Pirate #7
• James Silverman - Executioner / Pirate #1
• Lauren Tom - Numbuh 3
• Billy West - Pirate #8 / Miniature Cyclops / Spider Clown Mailman / Beast Master
• Fred Willard - The Boogey Man

Creating the film was the first time that Maxwell Atoms had created anything with a length of over one hour. That, along with creating the regular season was challenging for him. Boogey Man was chosen as the villain for the film because he was a lesser villain that had a relationship with Grim. This was because Atoms was given the idea to follow a storyline similar to Star Trek II: The Wrath of Khan by a Cartoon Network representative.

The role of Numbuh 3 was originally supposed to be taken up by an entirely new Grim Reaper character, with Atoms having Pamela Anderson in mind for the character, as one of the crew members worked on Stripperella. Anderson was contacted and expressed interest for the role, but was ultimately rejected by the studio's casting department thinking that the actress wasn't marketable enough.^[1] Atoms created a shortlist of alternatives, including Marilyn Manson, Drew Barrymore, and Elijah Wood, while Cartoon Network proposed more high-profile actors such as Angelina Jolie.

Unable to decide on finding an actor to play the role in time for production, Atoms decided to use a character from a Cartoon Network series and picked Hoagie Gilligan (a.k.a. Numbuh 2) from Codename: Kids Next Door to serve as Grim’s replacement because his childish innocence would serve as contrast to the role of the Grim Reaper, and his presence would also serve as a tease for the upcoming crossover special The Grim Adventures of the Kids Next Door. However, at the suggestion of that show’s creator, Tom Warburton, this was changed to Numbuh 3 taking Grim’s place. Atoms also used some Nintendo references in the later part of this TV movie, such as when Boogey Man kidnaps Mandy he makes a "warp pipe" appear and its SFX is used when he goes into it.^[2]

The title track "Land of the Dead" was written and performed by Voltaire. It is Voltaire's second collaboration for The Grim Adventures of Billy & Mandy, the first being on the episode "Little Rock of Horrors" with the song "Brains!"; "Land of the Dead" would later feature as the opening track of Voltaire's albums Ooky Spooky and Spooky Songs for Creepy Kids. The film's end credits also feature "Boogie Wonderland" by Earth, Wind & Fire. The film is most famous for its original song "Scary-O".

The film was released on DVD by Warner Home Video in the United States on April 3, 2007. The DVD contains both anamorphic wide screen and modified full screen versions with 5.1 surround sound and regular stereo sound. Special features include the season three episode "Bully Boogie" -Boogey's debut episode- and interviews with the voice actors.^[3] As of 2023, it has yet to be available to stream on iTunes, Amazon Prime, and HBO Max (except in Latin America).

The film received generally positive reviews from critics. Dennis Prince of DVD Verdict reviewed the movie saying, "All told, Billy & Mandy's Big Boogey Adventure is a gift from Atoms, and an indulgence of all the goodness and gooeyness that has made the series a top draw on Cartoon Network. Despite the boogers, bare buttocks, and boorish humor, this court finds no real crime has been committed. Case dismissed".^[3] MaryAnn Johanson, of The Flick Filospher reviewed the movie saying "'Full-length movie. Full of boogers!' promises the blobby green sticker on the DVD. And it's true. But somehow, the tons of gross-out potty humor manages to be delightfully goofy -- perhaps it's the irresistibly cheerful spin cartoonist Maxwell Atoms puts on his demented twisting of kiddie cartoons"^[4] It was nominated for an Annie Award for Best Music in an Animated Television Production.^[5] Common Sense Media gave the movie 2/5 stars and is meant for kids over the age of 8 calling it "undeniably gross and just as undeniably funny".^[6] DVDverdict.com gave the movie a good review as well.^[7]

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• Billy & Mandy's Big Boogey Adventure at IMDb