Alistair Krei is in his office at Krei Tech Industries having sushi, served by a professional chef named Momakase. As he feasts, he realizes too late that his food was poisoned, and becomes paralyzed. Momakase also turns out be a master thief, who has come to steal a top-secret invention that Krei is keeping in his office.
At the Lucky Cat Café, Aunt Cass is hard at work. She serves her customers cappuccinos with cute animal faces in the foam. Just Hiro arrives home from school, and receives a call from his friends, Aunt Cass realizes top celebrity chef, Bolton Gramercy, is in her Café. She tries to talk to him, but he speaks very rude to her in return and goes back to reading his paper. Meanwhile, Hiro and Baymax arrive at Keir Tech, where Krei is recovering from the toxin he consumed. The team learns from Krei that Momakase stole half of a prototype gravitational disruptor. The other half of the device is hidden in another safe in Krei's office. As the team inspects the office, finding a lot of stuff chopped up by Momakase, Hiro receives a call from his Aunt wondering where he is. He told her he was going upstairs to study, and she found his room empty with only Mochi under the bed sheets. Hiro tells her that he meant the upstairs school library, and he is having a study group with his friends. Cass is not convinced and believes that Hiro is out bot-fighting. So she goes out to find him, armed with her cooking knives.
Aunt Cass arrives in Good Luck Alley and finds a place where she believes the bot-fights are taking place. She walks up to the thugs guarding the entrance, who check her bag. When they find her knives inside, they think she is a fighter and escort her inside. Cass is then given an apron and ends up in the arena of an underground cooking competition called "Food Fight". Cass is, at first, not interested in entering, but when she meets her opponent, Bolton Gramercy, who insults her again, she decides to compete. Cass and Gramercy's challenge is to make the perfect crème brûlée using gummy iguanas, cilantro, and ostrich eggs. They have thirty minutes to cook and present their dishes to the judges. The two chefs race against the clock to make their crème brûlée. They both finish with seconds to spare, and present their dishes to the judges. Gramercy, however, ends up burning his. The judges taste both crème brûlée, and after some quiet consulting Cass is declared the winner. Since Gramercy lost, he has to give away his knives to Cass. Meanwhile, Momakase is visited by Yama, who hired her to steal the gravitational disruptor. He is not pleased that she only stole half of the device, only to be reminded that he hired her to steal what was in Krei's safe. However, she agrees to steal the other half on the account of extra payment.
Hiro and Baymax arrive home very late, after doing some investigation with the team. Hiro is worried about what to say to Aunt Cass, only to discover that she is not home. Suspecting she went out looking for him, Hiro and Baymax almost head back out to find her, but Cass walks through the door moments later. Hiro is the first to expresses how worried he was not knowing where she went. Cass says nothing about where she went and goes to bed. The next night, Momakase returns to Krei Tech to steal the other half of the gravitational disruptor. She sneaks into Krei's office where Hiro, Baymax and Wasabi are waiting for her. Momakase users her martial arts and sword skills to fight the three heroes. Using graphene bladed weapons that are thinner than paper but stronger than steel, she instantly slices through their armor and escapes with the other half of the device. Meanwhile, Cass starts sneaking out every night to go food fighting. She becomes quite a competitor, especially when other chefs try to pull off some deceitful stunt to make her lose. She always comes out victorious and claims the knives of her opponents. At the same time, she ends up oversleeping and keeps forgetting to open the Café on time. Pretty soon, Hiro starts to wonder where she keeps going every night. So, he and Baymax decide to follow her to Good Luck Alley and see what she is up to. Meanwhile, Momakase is visited by Yama again, pleased that she got the rest of the gravitational disruptor. He is just about to pay her, but Momakase has decided to sell the device on the black market for a higher profit. She then poisons Yama with toxic sushi and has him sent home before heading down to challenge Cass.
Hiro and Baymax find Cass in the cooking arena, just as Momakasei shows up. Hiro and Baymax are then thrown out, but call in the rest of the team. While Cass and Momakasei are busy competing against one another to make sushi in record time, Big Hero 6 go upstairs to retrieve the gravitational disruptor which is under guard. Momakasei tries everything to make Cass lose, but all her efforts backfire. She then notices a commotion going on in her office. Before heading upstairs to check it out, she finishes her dish and presents it to the judges. She also traps Cass in a net, so she cannot get her dish to judges before the time runs out. Big Hero 6 beat Momakase's men and retrieve the gravitational disruptor. However, Momakase shows up and engages the heroes in a fight. Wasabi has the gravitational disruptor and accidentally activates it when Momakase attacks him. Everyone at the fight ends up floating in zero gravity. Cass gets free and presents her dish to the judges with just a second to spare. She is declared the winner once again, much to Momakase's chagrin. She attacks Cass but gets caught in her own net just as Hiro deactivates the disruptor, restoring the gravity. Later, Momakase is arrested and the gravitational disruptor is returned to Krei. Chef Gramercy also apologizes to Cass for his behavior towards her, and she gives back his knives.
- Ryan Potter as Hiro Hamada
- Scott Adsit as Baymax, Goon #2, Boba Customer
- Génesis Rodríguez as Honey Lemon
- Khary Payton as Wasabi, Goon #1, Man in a Suit
- Jamie Chung as Go Go Tomago
- Brooks Wheelan as Fred
- Alan Tudyk as Alistair Krei
- Maya Rudolph as Aunt Cass, Pink Hair Woman
- Gordon Ramsay as Bolton Gramercy
- Alton Brown as Yum Laboughé
- Paul Briggs as Yama
- Diedrich Bader as Felony Carl
- Naoko Mori as Momakase
- In the scene where Baymax examines the numb Krei, his access port is on the right side of his chest.
- When Cass heads out to find Hiro, she takes a bag and a coat, but when she is in Good Luck Alley she only has her bag. It could be a filming error or Cass simply left her coat at home when she packed her cooking knives.
- In the scene where the thugs escort Cass to the Food Fight arena, her shoes and the cuffs on her pants are white. Cass' shoes are white again during the montage scenes of her competing in the Food Fight competition.
- When Momakase presents the whole gravitational disruptor to Yama, part of her hair is missing color.
- The US premiere date for this episode was leaked for March 22, 2018, but Bob Schooley confirmed that this announcement was not the official premiere date.
- This episode guest stars British chef Gordon Ramsay (whose character is also modeled after him) and food show presenter Alton Brown.
- Momakase's name is based on the Japanese phrase "Omakase", which is a type of meal consisting of dishes selected by the chef in a Japanese restaurant.
- Food Fight is a parody of various cooking shows such as Iron Chef America and Cutthroat Kitchen, both of which are hosted by Alton Brown, the voice of the host Yum Laboughe.