Sailor Moon: Little Nemo: Adventures in Slumberland

Sailor Moon: Little Nemo: Adventures in Slumberland is the movie crossover between Sailor Moon Crystal and Little Nemo: Adventures in Slumberland.

Plot
The film opens with the young boy Nemo experiencing a nightmare in which he is pursued by a locomotive. Upon awakening the next day, he goes with his pet flying squirrel, Icarus to see a parade welcoming a traveling circus. However, Nemo is unable to see the circus because his parents are too busy to take him. Usagi, Ami, Rei, Makoto, Minako and Mamoru appear from their future to meet Nemo when Minako learns Usagi's request to see Nemo for real. Later that night, Nemo imitates sleepwalking in a failed attempt to sneak some pie, going against a promise he had earlier made to his mother. Upon falling asleep that night, Nemo is approached by figures from the parade. The circus organist introduces himself as Professor Genius and claims that they had been sent on a mission by King Morpheus, the king of a realm named Slumberland. The mission involves Nemo becoming the playmate of the princess, Camille. Although Nemo initially has reservations about interacting with royalty of the opposite gender, he and Icarus decide to set off to fulfill his mission after being persuaded with a gift box of cookies from the princess.

Nemo is taken to Slumberland in a dirigible which he is allowed to drive, causing some chaos and is introduced to King Morpheus, who doubles as the circus ringmaster on Earth. Morpheus reveals that he summoned Nemo to become his heir to the throne. Morpheus gives Nemo a golden key that opens every door in the kingdom, and warns him of a door with a dragon insignia that must never be opened. Usagi, Mamoru, and other Guardians learn about the evil Nightmare King, ruler of the dreaded Nightmare Land. He attacked the kingdom, and was sealed away by King Morpheus and locked behind a giant door which all residents of Slumberland were forbidden to open lest the evil king be set free again. Nemo is introduced to Princess Camille and the pair and Icarus roam the entirety of Slumberland together. Afterward, Nemo is whisked away by Genius to prince lessons. Later, he meets the mischievous clown, Flip, who angers a group of cops and forces him and Nemo to hide out in a cave. There, Nemo discovers the door that Morpheus warned him not to open. Flip tempts Nemo into unlocking the door, which unleashes the dreaded Nightmare King. Nemo rushes back to Morpheus' castle in time for his coronation ceremony, where Usagi and Mamoru become Princess Serenity and Prince Endymion and Nemo is handed the royal scepter, the only thing capable of defeating the Nightmare King should he ever return to Slumberland. Prince Endymion dances with Princess Serenity and says that the Nightmare King is more dangerous than he thought and must conquer Slumberland to take over the Dream World, and that King Morpheus wants Nemo to help defend his kingdom. In the middle of a dance session between Morpheus and Genius, the Nightmare King reaches the castle and steals Morpheus away. As the partygoers search for a scapegoat, Flip and Nemo reveal each other responsible for the Nightmare King's escape, since Morpheus gave Nemo the key and it was Flip's idea to open the door.

Nemo then awakens in his home, which floods with seawater and ejects him and Icarus into the ocean. Genius reunites with them and tells Nemo not to blame himself and that Flip is to blame for all that has happened; Nemo refutes this, citing that he's the one who made and then broke his promise to Morpheus to never open the door, and resolves to find and rescue the king. When the three return to Slumberland and narrowly prevent Flip's banishment, Nemo forces Flip to reveal that he has a map to Nightmare Land, where Morpheus is currently being held. Usagi and her friends transform into the Sailor Senshi, revealing their secret identities to Nemo, Camille, Flip, and Genius. Sailor Moon, Sailor Mercury, Sailor Mars, Sailor Jupiter, Sailor Venus, Nemo, Icarus, Camille, Flip, and Genius set off in a tugboat in search of Morpheus. They are soon sucked into a whirlpool and find themselves in the monster-infested Nightmare Land. The five come across a group of shapeshifting goblins who wish to aid in the quest to rescue Morpheus.

The Nightmare King sends a flock of fearsome and gigantic goblin bats to seize the rescue party. Nemo attempts to use the scepter, but is unable to remember the full incantation and awakens in his bed along with Icarus just after watching Flip, Genius, and Camille be captured by the Nightmare King's forces. The goblins appear in Nemo's room and reunite with a lost member of theirs, who gives Nemo a letter from Morpheus containing the scepter's incantation to defeat the Nightmare King. The group returns to Nightmare Land by flying on Nemo's bed through a dimensional portal in the sky, and soon reach and infiltrate Nightmare Castle. However, they are subsequently trapped in the castle, where the Sailor Guardians are waiting and the Nightmare King demands possession of the scepter and threatens Flip, Genius, Camille, and Morpheus, whom are all in suspended animated states, with harm if Nemo doesn't comply. After a fierce battle, Sailor Moon and Nemo soon combine their powers and use the scepter and the Silver Crystal to finally defeat and destroy the Nightmare King and purify his kingdom, though due to Nemo's young age, the use of the scepter inadvertently kills him as well. As everyone awakens in the aftermath and discovers Nemo's lifeless body, they, along with the Sailor Guardians, begin to mourn for Slumberland's fallen prince. Morpheus, however, uses the scepter to restore Nemo to life. Nemo apologizes for breaking his promise, opening the door, and causing everything to begin with, but Morpheus forgives him, citing that his courage and strong will have allowed him to make up for his mistake, and become a true prince.

As Slumberland celebrates the fall of the Nightmare Kingdom, Camille escorts Nemo and Icarus home on the dirigible. The two share a kiss after which Nemo awakens in his room, where he apologizes to his mother for breaking his promise and trying to take the pie. Nemo's parents also agree to take Nemo to the circus along with Usagi, and her friends. Nemo stares out the window with Icarus as he reflects on his adventure.

Sailor Senshi

 * Stephanie Sheh as Usagi Tsukino/Sailor Moon
 * Kate Higgins as Ami Mizuno/Sailor Mercury
 * Christina Vee as Rei Hino/Sailor Mars
 * Amanda Miller as Makoto Kino/Sailor Jupiter
 * Cherami Leigh as Minako Aino/Sailor Venus
 * Michelle Ruff as Luna
 * Johnny Yong Bosch as Artemis
 * Robbie Daymond as Mamoru Chiba/Tuxedo Mask
 * Sandy Fox as Chibiusa Tsukino/Sailor Chibi Moon
 * Veronica Taylor as Sailor Pluto/Setsuna Meioh
 * Erica Mendez as Sailor Uranus/Haruka Tenoh
 * Lauren Landa as Sailor Neptune/Michiru Kaioh
 * Christine Marie Cabanos as Sailor Saturn/Hotaru Tomoe

Characters of the movie

 * Gabriel Damon (Takuma Gōno in the Japanese adaptation) as Nemo: He is a human boy living in New York City who is taken to Slumberland to be the official playmate of Princess Camille; in actuality, however, he is being summoned to be the heir to the elderly King Morpheus. He is given the key to Slumberland, but is warned by the king to leave a door with a coiled dragon emblazoned on it closed. Sadly, he opens the aforementioned door when he is tempted by Flip and goes on a quest to restore Slumberland to its rightful glory, save King Morpheus and defeat the Nightmare King.
 * Mickey Rooney (Chikao Ōtsuka in the Japanese adaptation) as Flip: He is described as a "frightful fellow" by Professor Genius, he is wanted throughout Slumberland for "having fun" (the bounty on his head is a sizeable one) and his only friend is his partner-in-crime: a bird named Flap. He tricks Nemo into accidentally releasing the Nightmare King and blames Nemo for the ruin of Slumberland. He is in possession of a map of Nightmare Land (hand-drawn and written in his own special code) and serves as the guide to the Nightmare Castle until he is replaced by the Boomps. He has a serious smoking addiction. In the real world, he is a clown in a circus that stops in Nemo's town.
 * René Auberjonois (Kōichi Kitamura in the Japanese adaptation) as Professor Genius: King Morpheus' advisor. He comes to the real world to bring Nemo to Slumberland. As a sophisticated man, he is quite punctual and prefers order as opposed to madness. He is quite a dancer, as he dances quite a bit during Nemo's coronation ceremony. In the real world, he is an organ player in a circus that stops in Nemo's town.
 * Danny Mann as Icarus: a flying squirrel, Nemo's best friend and a supporting protagonist. Icarus is Nemo's only friend from the real world. He shows great concern for Nemo's wellbeing in a sense similar to that of two siblings. He speaks a mix of both squirrel and some English. His screech is painful to the ears of the Boomps. He detests being called a "little rat" (which Princess Camille mistakes him for). Unlike other squirrels, Icarus eats human food, like cookies. His initial relationship with Princess Camille, though rough, eventually changes for the better.
 * Bernard Erhard (Kenji Utsumi in the Japanese adaptation) as King Morpheus: the elderly sovereign of Slumberland. He has protected Slumberland for years with the help of the royal scepter: an ancient weapon of great power. Though he is a child at heart, he knows when to be serious. He has Nemo brought to Slumberland so that he may become his heir to the throne. He gives Nemo the key to Slumberland, which can open any door; however, he warns Nemo of one door with a dragon symbol emblazoned on it that must never be opened. Like Professor Genius, he is quite a dancer, as he dances alongside the Professor during Nemo's coronation ceremony. When Nemo accidentally releases the Nightmare King, King Morpheus is captured and Nemo has to go and rescue him from Nightmare Land. In the real world, he is the ringmaster of a circus that stops in Nemo's town.
 * Bill Martin (Tarō Ishida in the Japanese adaptation) as the Nightmare King: He is a demonic creature who was locked behind a massive door until he was accidentally set free by Nemo, who was given the key to the door by King Morpheus. Once free, he captures King Morpheus as revenge for his imprisonment and then retreats to the Nightmare Castle in Nightmare Land. When Nemo goes to Nightmare Land to save King Morpheus, the Nightmare King has his minions capture Nemo's friends (Professor Genius, Flip and Princess Camille). He is shown to be quite temperamental, as he destroys several minions for the failure of just one of his underlings (the general of his army). The only thing that can vanquish him is the legendary royal scepter.
 * Laura Mooney (Hiroko Kasahara in the Japanese adaptation) as Princess Camille: the daughter of King Morpheus. Though she initially acts somewhat spoiled, she eventually grows to like Nemo. She also grows fond of Icarus (and vice versa, despite a rough start). When her father is kidnapped by the Nightmare King, she takes over as sovereign but decides to join Nemo in his quest to save King Morpheus. In the real world, she is the daughter of the ringmaster of a circus that stops in Nemo's town.
 * Greg Burson (Tesshō Genda in the Japanese adaptation) as Nemo's father and Flap
 * Jennifer Darling (Mari Yokō in the Japanese adaptation) as Nemo's mother
 * Neil Ross (Hiroshi Ōtake in the Japanese adaptation) as Oompa
 * Alan Oppenheimer (Keiichi Nanba in the Japanese adaptation) as Oomp
 * John Stephenson (Masaharu Satō in the Japanese adaptation) as Oompo and the Dirigible Captain
 * Sidney Miller (Kōzō Shioya in the Japanese adaptation) as Oompe
 * Michael Bell (Hiroko Emori in the Japanese adaptation) as Oompy
 * Kathleen Freeman (Kimie Nakajima in the Japanese adaptation) as the dance teacher
 * Bever-Leigh Banfield (Seiko Nakao in the Japanese adaptation) as the woman
 * John Stephenson (Kazumi Tanaka in the Japanese adaptation) as the dirigible captain
 * Bert Kramer (Yukimasa Kishino in the Japanese adaptation) as a goblin: A hideous creature that serves as a member of the Nightmare King's army. They are sent by the Nightmare King to ensure that Nemo doesn't reach his castle and free King Morpheus. Though the goblins succeed in capturing most of Nemo's friends, they fail to capture Nemo himself and, when the Nightmare King finds out, he kills them all in a fit of rage. The only goblins to survive are the Boomps (who, in contrast to the other goblins, are not hideous and are actually good).
 * Beau Weaver (Tarō Arakawa in the Japanese adaptation) as a policeman
 * Sherry Lynn as Bon Bon
 * Guy Christopher as a Courtier and a Cop
 * Nancy Cartwright and Ellen Gerstell as pages
 * Tress MacNeille as an elevator creature
 * Michael McConnohie as an etiquette master
 * Michael Gough as a teacher
 * Michael Sheehan as a fencing master
 * June Foray as the librarian
 * Gregg Berger as the equestrian master