"Halloween" is a Halloween-themed episode from the second season of the animated TV show The Amazing World of Gumball. It first aired on Cartoon Network in the United States on October 23, 2012 and aired in the United Kingdom on October 31, 2012.
It is Halloween at Elmore, and many of its residents are going trick-or-treating from house to house. At the Wattersons', Gumball voices his disapproval of Anais' princess costume, arguing that Halloween is meant to be scary. Anais counters by saying cute costumes earn more candy. Darwin, meanwhile, is white and shaken out of fear of Halloween. The group moves out, a worried Nicole frantically warning them to be careful and to return by seven o'clock. As the eldest child, Gumball is charged with watching over his siblings.
The trio ends up wandering into a cemetery, which Gumball says is a shortcut to a place filled with candy. An abandoned, haunted house stands over the distance, which he labels their "destination". Darwin is flabbergasted by Gumball's sense of direction, while Anais questions how much candy they can earn from the house. Gumball reveals his true intentions in full: each year, the house hosts a party for the undead. A ghost named Carrie warps in to elaborate on the annual festivities and the undead attendees. Darwin, still shaken, voices his objection, but Gumball reminds him of his authority, to Darwin's disdain. Conversely, Anais is enthusiastic about going to the party. Carrie disapproves of her babyish outfit, and Gumball wholeheartedly agrees, hanging Anais on a tree in the process.
Carrie, Gumball, and Darwin continue on to the house, which appears desolate at first. Carrie warns them not to tell anyone they are alive, and something else that is inaudible. She repeats herself twice; on the second time, Darwin yells at her to speak louder. Carrie tells them to drink one, and only one drop of a mysterious potion. Darwin reasons that anything that must be consumed only in minute quantities can be disastrous. Gumball blindsides him by flicking a drop into his gaping mouth. Darwin instantly goes wide-eyed and stares blankly into the room, causing Gumball to rethink drinking the potion. Darwin, however, forces a drop of the potion into Gumball's mouth, unveiling the party in progress and many undead creatures.
Anais, still dangling from the tree, is determined to get into the party. She shakes herself off the branch, only to fall straight into a deep well.
At the party, Carrie, Gumball, and Darwin mingle with the other ghosts. Carrie floats near a bowl filled with a strange substance, which Gumball takes interest in. The bowl contains ectoplasm, the very fiber of ghosts. Despite Carrie's warnings, Gumball immaturely demands for some, and a passing ghost obliges and gives him a glassful. The glass passes through his hand, and their mortality catches the attention of the partygoers. Gumball, thinking quick, consumes a large dose of the potion to turn into a ghost, but Darwin advises against it. After some peer pressure, Darwin yanks the bottle from Gumball's hands and takes a big swig himself. The two of them take turns gulping the potion down until Carrie stops them. Gumball and Darwin laugh at her, but are cut short when they turn into ghosts and lose their physical bodies. Darwin gives Carrie a spontaneous kiss and the party rages on. Elated by their ghostly appearances, the two hover off towards Elmore to cause their trademark mischief with their newfound capabilities.
Their escapades begin at the gas station, drawing a gruff face on Larry Needlemeyer to resemble a criminal on a wanted poster behind him. The Donut Cop arrives and mistakes him for the criminal, threatening him with his taser and arresting him. They then animate a moose head in the Robinson house, terrifying both Gaylord and Margaret. Their final prank is to possess Tina and wreak havoc on Elmore. However, controlling a dinosaur's body has proven to be difficult, and Gumball and Darwin instead make Tina fall on her face. The two depart, sounding off a T-Rex roar beforehand.
Having finally climbed out of the well, Anais rushes to the house and straight for the party. There, two ghosts find Gumball's and Darwin's lifeless bodies and use them as puppets. Anais sees this and looks confused. At the doorstep, she finds Carrie's potion bottle nearby and takes a sample of it, allowing her to see the undead.
Carrie tracks down Gumball and Darwin in time to warn them that if they do not return to their bodies by midnight, they will remain ghosts forever. The three race back to the haunted house, but as they reach the graveyard, a bell tolls to signal the passing of midnight. The ghosts return to their graves, and Gumball is grabbed by a zombie arm, prompting him to scream in terror. An enormous vortex opens up in the floor of the house, swallowing all undead to the afterlife. With renewed vigor granted by his sister's perilous screams, Gumball finds the courage to tear his pants off and run through the graveyard, dodging the army of zombie hands trying to pull him into the underworld. Darwin is caught by one and trips. Carrie fends off the ghosts, allowing Gumball enough breathing room to continue. She helps him up, but before they can do anything else, several more arms spring up to capture them. Darwin is on the verge of wetting himself, but Carrie is able to distract the arms long enough for him to run by. The arms attempt to pull her into the underworld, but because Carrie belongs to the mortal realm, they are unsuccessful.
Gumball manages to arrive at the house. To his horror, his sister is one slip away from being confined to the underworld. He takes this moment to apologize dramatically. Anais is both moved by his compassion and annoyed at him for wasting valuable time. Darwin arrives on the scene and notifies the siblings of their bodies slipping into the vortex. The three make a desperate leap to retrieve their bodies as the portal seals shut behind them.
With the house barren once again, Carrie begins to mourn for her friends. Miraculously, the gateway opens up and the three are spat back out, returned to their bodies. Nicole drives in, enraged that it was past midnight and they weren't home yet. As the three try to explain themselves, they discover that they are not in their respective bodies. They assure their mother that Carrie can get them back to normal, only for her to vanish after an awkward silence. The episode ends with Nicole confused and the Watterson children nervously eyeing one another.