The Grim Adventures of Billy and Mandy is a 20XX traditional hand-drawn American film produced by Walt Disney Animation Studios and distributed by Walt Disney Pictures in the United States and Japan (with Warner Bros. Pictures distributing the film elsewhere). It is based on the Cartoon Network series of the same name.
The film is the 70th animated film in the Disney animated film canon and is also the first film in the 2nd Disney Renaissance.
The idea for this film was created by BiggestKirbyFanEver1994.
Billy and Mandy, two seemingly ordinary kids, who spend their day celebrating the birthday of Billy's hamster, Mr. Snuggles, who is ten years old and close to the end of his life, especially due to years of abuse from Mandy. The Grim Reaper appears via a vortex to harvest the hamster's soul, but is dumbfounded that Billy and Mandy aren't afraid of him in the slightest.
Mandy tells Grim she won't let him take Mr. Snuggles because she enjoys torturing him. She challenges Grim to a game; if Grim wins, he will not only take Mr. Snuggles' life but also Billy's and Mandy's as well, but if he loses, Grim will be their best friend forever.
Grim decides to compete for the life of Mr. Snuggles over a game of limbo. Grim, not willing to let the children win, begins to cheat. As Grim is about to win, Mandy orders Mr. Snuggles to attack Grim, causing Grim to lose. As a result, Grim is forced to become Billy and Mandy's best friend.
Grim reluctantly settles in as Billy and Mandy torture him and he puts . Billy and Mandy are thirsty and decide to get a soda. The kids go in Grim's trunk. But in the trunk, there is an egg that Billy hatches, and a large spider named Jeff comes out and thinks Billy and Mandy are his parents. Billy get very scared of him and tries to squish him, but Mandy thinks Grim would be more miserable if he had to take care of Jeff, so they force Grim to babysit Jeff while Billy and Mandy go to school.
The next day, Billy and Mandy decide to bring Grim to school as part of Show-and-Tell. However, the students freak out and Mrs. Butterbean calls Animal Control to place Grim somewhere far away. Billy, Mandy and Jeff the Spider set out to rescue him.
In The Pound, Grim and a bunch of other creatures (including a cameo by Fred FredBurger) are locked inside tiny cages and many are making too much noise. Just then, a man named Warden Cage, who is in charge of The Pound, tells all the animals to "shut up and do as I say, or else you get-a-sprayin!!!" as he pulls out a water spray can. The animals suffer, but Grim actually enjoys it. In fact, he fells being inside a cage as even better than enduring Billy and Mandy.
Meanwhile, Billy and Mandy ride Jeff the Spider on their way to The Pound. However, Officer Rookie, an inexperienced police officer, notices the trio pass the speed limit and tries to arrest them. Fortunately, they outrun Rookie and his car crashes into a tree.
Billy and Mandy use Jeff as a battering ram to break through the gate, rescue Grim and proceed to escape. However, Warden Cage stops them in their tracks. Suddenly,Mr, Snuggles shows up to try to stop him but gets thrown into a tiny cage along with Billy, Mandy and Jeff. Mandy uses her headband to unlock the cage, freeing her, Billy, Jeff and Mr. Snuggles. They sneak past a sleeping Warden Cage to free Grim, but Grim refuses to be freed. After several minutes of arguing, they accidentally wake up Warden Cage and he pulls out an even bigger spray can called "Big Bertha". When he tells them any last words, Mandy yells "Kiss, kiss!" and Mr. Snuggles attacks Warden Cage. This gives time for Billy, Mandy, Grim and Jeff to escape.
Officer Rookie is in the police station ready to turn in his badge but notices Billy and Mandy once again speeding. This gives him the opportunity to redeem himself and goes after them. However, he ends up crashing into a car... again.
Back home, Grim argues that he doesn't belong with Billy and Mandy, but they tell him he has no choice, but after some thinking, Mandy actually decides to make the experience less miserable for Grim by allowing him to take a day off once a month. Grim celebrates by singing "Under the Sea" from The Little Mermaid.
The film ends with Billy and Mandy questioning Grim's musical number, Billy saying "I have NO idea, and that's sayin' a lot, since I always have no idea what goes on on a regular basis." Mandy simply says "Eh... I'll take your word for it." as the screen fades to black. Billy then asks "So.... now what?". Mandy says "Let watch the credits roll, I guess."
The credits play with the song "Monster Mash" playing in the background.
After the credits, Mandy walks in and says "You're STILL here? Get out. The movie's over, you know. It's not like they're gonna make a Grim Adventures of Billy and Mandy 2..... Hey! Are you listening to me? I said 'Get out!' What do you want me to do? Smile?" and so Mandy smiles to get the audience to leave, but it is rather grotesque and a woman's scream is heard in the background. The screen fades to complete black and Mandy says "That should do it."
- Richard Horvitz as Billy
- Grey DeLise as Mandy
- Greg Eagles as Grim
- Maxwell Adams as Jeff the Spider
- C. H. Greenblatt as Fred FredBurger (cameo)
- Matthew Patrick as Officer Rookie (new character)
- James Rolfe as Warden Cage (new character)
- This is the first film in the Disney animated canon to be based on a show produced by Cartoon Network (this is why the film is distributed by Warner Bros. Pictures outside of the United States and Japan).
- The film is mostly a re-telling of The Grim Adventures of Billy and Mandy pilot episode "Meet the Reaper" and the Season 2 episode "The Crawling Niceness"; the third act is written exclusively for the film.
- The film's humor is reminiscent The Emperor's New Groove, Home on the Range and Season 1 of the original The Grim Adventures of Billy and Mandy series (due to it being a Disney film, it opts to avoid the humor of the later seasons as they are more raunchy and dark compared to the much tamer Season 1).
- Matthew Patrick (host of YouTube series Game Theory) and James Rolfe (creator of The Angry Video Game Nerd series) star as new characters created for this film.
- Mandy was originally meant to smile occasionally during the film, but it was later decided to have her smile in the post-credits scene.
- Warden Cage, one of the film's new characters, is named for the fact that he throws animals in cages. In addition, the other new character, Officer Rookie, is named for the fact he is a new (and rather inexperienced) recruit.
- A new educational TV series based on the film (and subsequently the original TV series), titled The Grammar Adventures of Baby Billy and Mini Mandy, will be in development for Disney Junior.