Mochi is usually calm but has hissed at Alistair Krei showing dislike for him. He is easily scared by sudden actions and likes to sleep in Hiro's bed.
After the Hamadas return home following another incident of Hiro's bot-fighting activities, Cass starts stress-eating donuts after lecturing the boys on their irresponsibility and goes to the kitchen, calling to a sleeping Mochi to come with her, to which the cat complies.
Later, when Hiro and Baymax return home after trying to investigate his Microbots' activity, Hiro tries to get Baymax upstairs without his aunt noticing. Mochi appears, purring and rubbing against Hiro, prompting Hiro to claim the sounds Baymax is making to be from Mochi. When Cass turns away again, Hiro throws the cat upstairs. When Hiro arrives in his bedroom, Mochi is seen being petted by Baymax and purring in his arms while calling him a "hairy baby". Mochi notices Hiro and leaves the room, still bitter about Hiro throwing him. When Hiro and Baymax sneak out again, Mochi is shown with Cass watching Frankenstein.
Mochi stars in the short "Baymax and Mochi", where Cass leaves Baymax to take care of him while she's out, but after giving him a mouse toy, the cat makes a mess all over Lucky Cat Café, so Baymax gives him a bath which Mochi despises.
Later, Baymax keeps trying to play with Mochi, but he gets dirty again so Baymax gives him another bath. Mochi then goes into the chimney and once more gets dirty, so Baymax attempts to put him in the dishwasher for another bath, but this time Mochi escapes from the Café.
Baymax then follows him all over town, and in the end both return home. At night, Cass finds Baymax in his charging dock with Mochi sleeping in his arms.
Mochi appears in the series (usually with Cass or at the Café) but has his first major role in "Mr. Sparkles Loses His Sparkle". In the episode, Mochi learns how to clap slowly with his paws, and Honey Lemon records him then uploads the video to the internet. The video becomes a hit due to its cuteness and Mochi becomes famous. However, the video inadvertently causes Mr. Sparkles' popular internet challenge show to lose fans, which makes him angry and jealous of Mochi.
Mr. Sparkles finally snaps when people put him aside to take photos of Mochi, so he goes and captures the cat while Cass is being interviewed, places him in a rocket and announces that he'll launch it into the sun unless someone completes one of his challenges. Hiro tasks Baymax to go with Cass and prevent her from finding this out. Both go around San Fransokyo pasting "Missing" flyers while Hiro builds a robot to save him and the rest of Big Hero 6 try to get the challenge done. Go Go succeeds but Sparkles had gone mad enough to launch him regardless, right before escaping. Fortunately, Hiro arrives in time and sends his new robot, Skymax, to bring back Mochi.
After Mochi is saved, his reunion with Cass is recorded and posted to the website MeowTube where the video becomes another hit as well.
Mochi watches the café with Honey, Wasabi, Fred, Baymax, and Mini-Max when Cass had to attend to a catering event. Mochi runs away into San Fransokyo which leads Fred, Baymax, and Mini-Max to search for the lost cat. They finally locate Mochi at San Fransokyo Bridge at the same time Hiro, Go Go Tomago, and Krei were being tailed by a mutated Ned Ludd. The team engages the Hibagon and are overwhelmed until Mochi contributes, and proves instrumental in the Hibagon's defeat, as his claw swipes knock off the transdermal patch that caused Ned's transformation, turning Ned back to normal. He returns to the café with an exhausted team after the battle.
- Mochi - Mochi is a Japanese rice cake that is filled with a flavored paste. It is a popular treat and can be filled with bean paste or ice cream. Mochi is usually made in a special mochitsuki ceremony, and is usually served around the Japanese New Year.
- Early designs showed Mochi with rockets on his paws, giving him the ability to fly. This concept was removed for Mochi but appeared in the film as a separate cat seen at the San Fransokyo Institute of Technology, whose owner resembled Tony Stark.
- Mochi actually got to use these rockets in the Big Chibi 6 short titled "Mochi No!"
|Big Hero 6: The Series shorts|
|1. "Baymax and Fred":||Appears||4. "Baymax and Hiro":||Appears|
|2. "Baymax and Go Go":||Absent||5. "Baymax and Mochi":||Appears|
|3. "Baymax and Wasabi":||Absent||6. "Baymax and Honey Lemon":||Absent|
|1. "Baymax Dreams of Evil Sheep":||Absent||3. "Baymax Dreams of Too Many Baymaxes":||Absent|
|2. "Baymax Dreams of Bed Bugs":||Absent|
|Big Chibi 6|
|1. "Making Popcorn":||Absent||7. "Love Letters":||Absent|
|2. "Mochi No!":||Appears||8. "Super Charged":||Absent|
|3. "Save Mochi":||Appears||9. "Low Battery":||Appears|
|4. "Noodle Song":||Absent||10. "Road Trip":||Absent|
|5. "Snoring":||Absent||11. "Super Driver":||Absent|
|6. "Gumball Trouble":||Appears||12. "Brunch Rush":||Absent|
|Baymax and Mochi|
|1. "Flowers and Butterflies":||Appears||2. "Mochi and his Toy":||Appears|
|Big Hero 6: The Series - Season 1|
|1. "Baymax Returns":||Appears||12. "Small Hiro One":||Absent|
|2. "Issue 188":||Absent||13. "Kentucky Kaiju":||Appears|
|3. "Big Roommates 2":||Absent||14. "Rivalry Weak":||Absent|
|4. "Fred's Bro-Tillion":||Appears||15. "Fan Friction":||Absent|
|5. "Food Fight":||Appears||16. "Mini-Max":||Absent|
|6. "Muirahara Woods":||Absent||17. "Big Hero 7":||Absent|
|7. "Failure Mode":||Absent||18. "Big Problem":||Absent|
|8. "Aunt Cass Goes Out":||Appears||19. "Steamer's Revenge":||Absent|
|9. "The Impatient Patient":||Pictured||20. "The Bot-Fighter":||Appears|
|10. "Mr. Sparkles Loses His Sparkle":||Appears||21. "Obake Yashiki":||Absent|
|11. "Killer App":||Absent||22. "Countdown to Catastrophe":||Appears|
|Big Hero 6: The Series - Season 2|
|1. "Internabout":||Absent||6. "The Fate of the Roommates":||Absent|
|2. "Seventh Wheel":||Absent||7. "Muira-Horror!":||Appears|
|3. "Prey Date":||Pictured||8. "Something Fluffy":||Appears|
|4. "Something's Fishy":||Absent||9. "Supersonic Sue":||Absent|
|5. "Nega-Globby":||Absent||10. "Lie Detector":||Background|