Mouserinks or simply the Mouse King is a a minor character from the 2018 movie The Nutcracker and the Four Realms. He is a magical being who lives in The Fourth Realm. His mission is to protect the Fourth Realm from the evil Sugar Plum Fairy. He is Mother Ginger's greatest friend and ally, and thus he becomes an ally of Clara Stahlbaum and Phillip the Nutcracker.
The Mouse King is based on the character of the same name from the story by E.T.A. Hoffman and the ballet by Pyotr Ilyich Tchaikovsky.
The Mouse King is first seen watching Clara exploring the Christmas Tree Forest around her and as she finds the key for Marie's last gift, he snatches it from Clara and chases her across the snowy landscape. Clara demands him to give her back the key to which he refuses to which while chasing him, Clara becomes distracted upon seeing a nearby nutcracker soldier named "Phillip". During a conversation between Phillip and Clara, the Mouse King drops the key in shock and runs towards the Fourth Realm.
Just as Clara and Phillip arrive at the Fourth Realm, Clara approaches the Mouse King and demands him to give the key back to her to which he refuses. Enraged, the Mouse King forms into a giant creature made out of thousands of mice and engulfs her in rage. Later, when Phillip notices the Mouse King who transformed into a giant mouse made out of thousands of mice and upon rescuing Clara, Phillip explains that the giant creature made out of thousands of mice is the Mouse King to which the two escape from him and his minions. The Mouse King and his army of mice retreat. Suddenly, the two notice Mother Ginger who is approaching the two just as Phillip explains that Mother Ginger could be a trap, just as he and Clara ride on Jingles to escape from her.
The next day, Clara leads an army to enter the forbidden Fourth Realm and face Mother Ginger as the Mouse King notices the army passing by. As Phillip and Clara escape from Mother Ginger with the key for Marie's last gift, Mouserinks, the Mouse King, is sent to the Palace by orders of Mother Ginger, noticing what Sugar Plum has done to the Four Realms. However, it is found out that the Mouse King, alongside Mother Ginger, was betrayed by the Sugar Plum Fairy. The Mouse King then escorts Clara and Phillip to escape. Devising a plan to enter the Engine Room, the Mouse King agrees with Clara's plan just as the two plan to go to the Engine Room and stop Sugar Plum from destroying the Four Realms. When Phillip arrives at the Fourth Realm to alert Mother Ginger about Sugar Plum who is summoning an army of tin soldiers to destroy the Four Realms, the Mouse King becomes a giant creature made out of thousands of mice once again just as he and his minions fight against the tin soldiers. The battle, however, was successful
After Sugar Plum is transformed into a porcelain via Engine, Phillip, the Mouse King, and the rest of his minions celebrate their victory with the Four Realms saved. Back at the Palace of the Four Realms, Phillip is accompanied by the Mouse King as his new friend for protecting the Four Realms.
- In both the original story and the ballet, he was the main villain. Here, he is a heroic figure, while The Sugar Plum Fairy is the main villain instead (who, in turn, was a heroic figure in the original story and in the ballet).
- In the book, he actually had seven heads. In the film, he has only one like all real-life mice.
- In the film, he and his subjects become one huge mouse to defeat enemies bigger than they which is not at all in the book.
- The name "Mouserinks" actually originated from the character Madam Mouserinks (also known as the "Mouse Queen") from the original Nutcracker story where it is known the original unnamed Mouse King was the son of deceased Madam Mouserinks, a character who was with Princess Pirlipat in a story where Drosselmeyer tells a story to the protagonist Marie (Clara) about how nutcrackers came to be.