Mother 4: The New Pig King, also known as Mother 4: The Four Heroes, is a fanon game in the Mother series and takes place presumably before the events of Mother 3. It tells the story of Gavin, a twelve-year-old boy who, after the kidnapping and re-animating of his sister Judy, is called upon to stop the strange army, the Pigmasks and their new leader, Winston.
After waking up, Gavin is surprised from his sisters disappearance. Listening to his mother and aunt's conversation about their wealth, he leaves his home to find her. He comes across his neighbour, Felix's, house, who, with almost no resentment or question, decides to help him find her. They travel to the end of the valley, where a strange flying contraption has landed. Winston, and a presumably weird character in a pig's mask, have captured Judy and fly away with haste, leaving Gavin and Felix to battle a gigantic robot they created. Shortly after, Gavin, in complete and utter shock of this event, runs home without Felix. Eventually, Gavin and his family move from the valley to the nearby Castle City, where they ignore Gavin and try to take better care of their wealth.
The camera pans to Louie, an employee of Pascal's Pizza Parlour, who leaves after a very short day of work. Noticing the state of the nearby theatre, he helps the band inside, the Rolling Beats, who promise to help him when they can. Shortly after, however, Louie gets kidnapped by the local thugs, the BULL.Es, and is kept prisoner in their headquarters with a young girl named Cindy. The town is soon outraged by the disappearance of Cindy, making this a prime time for Gavin to escape from his house, and he locks himself in the BULL.Es headquarters. Louie and Cindy manage to escape, finding Gavin at the enterance, and Louie safely return her to her parents. Although Louie recommends Gavin heads home too, after some explaining Louie understands and decides to see if he can help him. The two go to the mayor's building and go to the top, where they find Winston and his maid Maria. Winston takes off in a similar helicopter from before, and leaves an almost complete reconstructed version of Judy to kill Gavin and Louie. Although they manage to defeat her, Gavin is shaken up by the event.
The player then takes control of Chloe, a student at the school in her hometown of Oxford, and her best friend Vicky. The two hear knocking at the school gates and answer it, finding Winston, pretending to be the son of the owner of the mansion in Burgundy Forest, and asks Chloe and Emily for help getting there. Chloe resents at first, but Emily agrees and Chloe is left to trail behind. Once they get there, Winston manages to lock the two inside. In an attempt to get out of the mansion, Emily gets knocked out-cold, and Chloe drags her to the bedroom to take care of her. She sends a psychic message to someone pleading for help, which Gavin recieves, but when he and Louie arrive, the building is already being invaded by the Pigmasks. They manage to get past them, however, the Pigmasks manage to kidnap Vicky and almost get away with her, but she slips away at the last second. Gavin, Chloe and Louie, in an attempt to save her, anger the spirit of the mansion, Sir Bravery. After defeating him, they realize they've been locked in once again, and Chloe sends another psychic message to someone. Amir, son of Andrew and worker of the desert, listens upon her words and, ignoring his father's orders, runs to Burgundy Forest. Coming across Vicky first, the two go to the mansion where they find a strange, white Pigmask opening the door for them. The Pigmask quickly flees. After a little discussing, Amir agrees to join Gavin and Louie, and Chloe decides to ask her principal, Mr Cartwright. He allows her to go, and Vicky says goodbye to her.
The player then takes control of Pigmask Colonel, the white pigmask from before. The Colonel speaks to a great crowd of Pigmasks, and talks about the new leader (Winston) and has the upmost faith in him. However, shortly after the event, he recieves a call from Winston, asking to meet him in another room. He does and, with meeting him for the first time, he discovers he is a child and starts to lack faith in him. Winston informs him about the four heroes and the location of one of them, Judy, located in the grassy valleys north of Castle City. They travel there by helicopter and the Colonel kidnaps her from her home.