Big Hero 6 vs. the Forces of Evil is a 2017 American animated superhero comedy adventure crossover film, set between the universes in the 2014 Disney film, Big Hero 6, and the Disney XD series, Star vs. the Forces of Evil. It premiered in the United States on January 16, 2017 on Disney XD.
Many years ago, the people of Mewni were at war with monsters, lead by their leader, Zorona. Eventually, the people of Mewni won the war, declaring their "Mewnipendence", and the monsters lost. The loss lead to Zorona being banished to the Spirit dimension. Zorona swears one day she will make a return and cause chaos everywhere.
Several years later, Star Butterfly wakes up her best friend, Marco Diaz, to celebrate National Best Friends Day. The two spend the entire day doing countless activities, and ending it fighting monsters. The next day, a mysterious new student named Melanie arrives at Echo Creek Academy. Marco gets her attention and shows Melanie around the school. Star begins to feel suspicious about Melanie's actions. In the next five days, after Melanie begins to third-wheel Star and Marco's friendship, Star snaps and nearly casts a lethal spell on Melanie. Marco confronts Star and tries to tell her to stop, which leads the two to start arguing with each other. Star angrily grabs her dimensional scissors and opens a portal to a random realm. Star leaves Marco and Melanie behind without saying a word.
Star makes her way out of the portal, only to find herself in a city called San Fransokyo. After walking around the city, she meets a big, white, inflatable robot named Baymax. In need of a new best friend, Star takes Baymax to the Bounce Lounge dimension to have some fun. Meanwhile, robotics prodigy and superhero Hiro Hamada feels left out because his "adult" friends, GoGo, Wasabi, Honey Lemon, and Fred, are attending a convention that's exclusively for adults. This results in Hiro wishing he had friends his own age. Hiro later panics when he notices that Baymax is missing. When Hiro makes his way back home to his room, a portal opens with Star and Baymax hopping out of it. A frightened and confused Hiro asks what's going on. Star, not wanting to cause anymore trouble, decides to leave and go back home. Hiro realizes that he's missing his chance to have a friend his own age and chases after her. Before Star opens a portal to home, another portal opens up with a 90 ft tall monster jumping out of it. When the monster begins attacking the city, Star jumps into action and fights the colossal beast. Hiro and Baymax get into their superhero gear and assist Star. After Star, Hiro, and Baymax defeat the monster, the entire city cheers for Star and declares her a new hero.
Meanwhile, back at Echo Creek, Marco begins to worry about Star. Melanie reassures Marco into telling him that Star is okay. After Marco leaves for a karate tournament, Melanie transforms to Zorona, revealing her true self. It is shown that Zorona used the All Seeing Eye relic to track Star's location, revealing that she sent the monster to San Fransokyo to kill Star. When she discovers that Star slayed the monster, a furious Zorona opens a portal to San Fransokyo to kill Star herself.
Back at San Fransokyo, Star, Hiro, and Baymax become best friends. While taking a stroll around town, many people congratulate Star and hands them out free stuff. While dining at Aunt Cass' cafe, many people, including Aunt Cass, mistake Star for being Hiro's new girlfriend. An embarrassed Hiro walks upstairs to his room, while Star playfully follows him. Star asks Hiro if he could build her a superhero suit too. Hiro, while staring at an old photo of him and his late brother, Tadashi, agrees and heads over to the garage. After completing the suit, Star gives it a test drive. She sends herself flying towards the sky. Hiro and Baymax get into their gear and chase after her. Star begins to fly around San Fransokyo, with Hiro and Baymax still following her. After the three land on top of a building, Hiro realizes how happy he's made Star. Star thanks Hiro by taking him to the Spirit dimension to reunite with Tadashi. After the reunion, the three friends return home.
The next day, Hiro's friends return home from their convention. After they meet Star, Zorona also arrives and gets ready to attack Star. Star, Hiro and his friends quickly get into their suits and try to defeat Zorona. Towards the end of their battle, Zorona destroys Star's suit and takes her wand. Zorona then opens a portal and heads over to Mewni. Meanwhile, after Marco returns home from his karate tournament, he notices the All Seeing Eye and sees that Star is in trouble. With help from Glossaryck, Marco heads on over to San Fransokyo. When he gets there, Star, who has lost all faith, tells Marco what happened. After Marco and Hiro persuade Star to go after Zorona, Star finally gets up on her feet and goes after her. Marco and the Big Hero 6 go with her to help.
Over at Mewni, Zorona uses Star's wand to unleash a spirit army from the Spirit dimension and terrorize the kingdom. While the army attacks the citizens, Zorona heads on over to the castle and hold King and Queen Butterfly hostage. Star, Marco and the Big Hero 6 arrive to the scene. Hiro orders Marco and the other four to fight the army while, he, Baymax, and Star go after Zorona. At the castle, Baymax uses his rocket fist to push Zorona against the wall, forcing her to let go of Star's wand. Star grabs her wand and has a one on one battle with Zorona while Hiro and Baymax bring Star's parents to safety. The fight leads to Star and Zorona on top of the castle. Zorona grabs Star by her neck and opens a portal to the Spirit dimension. Before she throws Star in there, Star casts a spell on Zorona and her army. As Star jumps off the castle, Zorona and her army begin to disintegrate. King and Queen Butterfly and the people of Mewni cheer for Star, Marco, and the Big Hero 6.
Back at San Fransokyo, Star and Marco embrace and apologize to each other. Before they head back home to Echo Creek, Star gives Hiro a mirror so he can be able to contact her anytime he wants. The six wave goodbye to Star and Marco as they head through the portal.
The film closes with Star and Marco eating a smorgasbord of junk food.
- Eden Sher as Star Butterfly
- Ryan Potter as Hiro Hamada
- Scott Adsit as Baymax
- Adam McArthur as Marco Diaz
- Zoe Saldana as Zorona, the evil spirit from a thousand years ago who tries to take over all of Mewni.
- Jamie Chung as GoGo Tomago
- T.J. Miller as Fred
- Damon Wayans, Jr. as Wasabi
- Génesis Rodríguez as Honey Lemon
- Maya Rudolph as Aunt Cass
- Artt Butler and Nia Vardalos as Mr. and Mrs. Diaz
- Alan Tudyk as Ludo and King Butterfly
- Grey Griffin as Queen Butterfly
- Jeffrey Tambor as Glossaryck
- Daniel Henney as Tadashi Hamada
- Tony Anselmo as Donald Duck
The film premiered in the United States on January 16, 2017 on Disney XD. The film will feature music from Diplo and Imagine Dragons.
Big Hero 6 vs. the Forces of Evil received positive reviews from critics and fans alike. On Rotten Tomatoes, the film received a rating of 83%, based on 30 reviews, with an average rating of 7.5/10.
A sequel, Big Hero 6 vs. the Forces of Evil 2: Miraculous Squad, was released on July 7, 2017. As the subtitle implies, the film also crossovers with the French animated series, Miraculous: Tales of Ladybug & Cat Noir.