Rosemary Hills 8: Mewtwo Strikes Back is a 2021 American animated adventure fantasy film based on the animated television series Rosemary Hills. The film was released in theaters on December 24, 2021.
Scientist Dr. Roman is hired by Gomez, leader of Zora and her henchmen, to utilize his expertise in cloning in order to create a living weapon based on an eyelash from mythical Pokémon Mew. Roman is revealed to be allying with Gomez as a means to fund his side project: the resurrection of his deceased daughter Trudy. In a laboratory, the weapon eventually gains sentience and is named Mewtwo. Mewtwo befriends the salvaged consciousness of Trudy, named Trudytwo, as well as the clones of other Pokémon in the laboratory. However, Mewtwo is left deeply traumatized after Trudytwo and the rest of the clones decompose and die. In order to stabilize him, Roman tranquilizes Mewtwo, causing him to forget the time he spent with his friends.
After Mewtwo fully matures and awakens from a long slumber in a laboratory on New Island, he learns of his origin as Mew's clone from Dr. Roman. Infuriated that Roman and his colleagues see him as nothing more than an experiment, he unleashes his incredibly strong psychic abilities and telekinetically destroys the laboratory, killing Roman and the rest of the scientists. Gomez, witnessing the carnage afar, approaches and convinces Mewtwo to work with him to further develop and perfect his mental abilities. However, after Mewtwo learns of his purpose to be a weapon for Gomez's benefit, he escapes back to New Island where he plots revenge against humanity and Pokémon alike.
After Mewtwo rebuilds the laboratory and establishes a base there, he invites several trainers with hologram messages to battle the world's greatest Pokémon trainer at New Island. Milly and her friends receive a message and accept the invitation, but when they arrive at the port city, Old Shore Wharf, Mewtwo creates a storm, causing the boats on the wharf to be closed off for safety. As a result, Milly's group are picked up by Zora and her henchmen disguised as Vikings on a boat. After the storm sinks their vessel in the middle of the ocean, Milly and her friends use their Pokémon instead to reach New Island.
Escorted into the island's palace by the woman who appeared on the hologram, Milly and the other trainers who were able to reach the island encounter Mewtwo. The woman is revealed to be a brainwashed Miranda after she is released from Mewtwo's mind control. Mewtwo challenges the trainers using cloned Pokémon coincidentally modeled after the deceased friends from his childhood. Meanwhile, Zora and her henchmen also reach New Island and explore its inner sanctum with a Mew innocuously following them. After Mewtwo's clones effortlessly defeat the challengers' Pokémon, he confiscates them and expands his clone army. Milly chases after his captured Pikachu down the cloning lab, where Morty's Meowth is also cloned. Milly destroys the cloning machine, frees the captured Pokémon, and leads them to confront Mewtwo and his clones. Mew then reveals itself and Mewtwo challenges it in order to prove his superiority.
All of the Pokémon originals battle their clones save for a defiant Pikachu and Meowth, who makes peace with his own clone after realizing the senselessness of their fighting. Frustrated with the pain and anguish felt on both sides of the battle, Milly tells her friend Emmy to destroy Emmanuel, and his henchman Robert once and for all. Emmy agrees, and she takes Max, Amaya, Tevin, and Monica with her. Emmy even takes the Pokemon to destroy him. At the castle, Monica tells Emmy to use the Pokemon. However, the voice of Milly tells Emmy to let the Pokemon destroy Emmanuel. With the Pokemon using Water Gun, Emmanuel is destroyed once and for all. Robert tried to avenge him by attacking Emmy, but Monica knocked him into the acid, destroying him as well. Pleased by Emmy's bravery, Mewtwo realizes that he should not have to be judged by his origins but rather his choices in life. Departing with Mew and the clones, Mewtwo turns back time to just before the trainers leave Old Shore Wharf, and erases everyone's memories of the event.
Back in Old Shore Wharf, the now-restored Miranda has returned to reopen the Pokémon Center to shelter the trainers. The storm outside clears up, Milly spotting Mew flying through the clouds and tells her friends of how she saw another legendary Pokémon the day Ash Ketchum left Pallet Town. Meanwhile, Zora and her henchmen find themselves stranded on New Island but enjoy their time there.
After the credits, a brief scene shows Mew flying towards the mountains.
- Cathy Cavadini as Milly
- Tony Danza as John
- Chris Tucker as Tevin
- Jeremy Irons as George
- Emma Watson as Mina
- Rachel House as Miranda
- Tara Strong as Leo
- Kath Soucie as Leah
- Andrea Libman as Emmy
- Danny McKinnon as Max
- Haven Paschall as Paula Schaeffer
- Jen Tolley as Becky
- Tress MacNeille as Sandra
- Veronica Taylor as Wendy
- Scott Weinger as Jeff
- Common as Mewtwo
- Kristen Li as Trudy
- ??? as Dr. Roman
- Avril Lavigne as Lita
- Orlando Bloom as Christian
- Chris Platt as Freddy
- This is the first movie in which Amaya, Zora, Randy, and Morty appear in.
- This is also the first movie since Milly's Land in which Milly has the main role.
- This is the second time a movie has been released in 2021, the first being A Rosemary Land Life.
- Milly and her friends wear the attire from Rosemary Hills: Pokemon Adventures.
- Ash Ketchum is mentioned in this movie.