is a Crossover Between Wreck it Ralph & Big Hero 6. a Villain Named Yokai Steal Hiro's Mircobots With King Candy/Trubo, Kaos & Dr. Neo Cortex who is on Yokai's Side.
- Ryan Potter as Hiro Hamada, a 14-year-old robotics prodigy who has already graduated high school. His older brother Tadashi inspires Hiro to gain admission to San Fransokyo's Institute of Technology. Speaking of the character, co-director Don Hall said "Hiro is transitioning from boy to man, it’s a tough time for a kid and some teenagers develop that inevitable snarkiness and jaded attitude. Luckily Ryan is a very likeable kid. So no matter what he did, he was able to take edge off the character in a way that made him authentic, but appealing.
- Scott Adsit as Baymax, an inflatable robot built by Tadashi to serve as a healthcare companion. Hall said "Baymax views the world from one perspective—he just wants to help people, he sees Hiro as his patient." Producer Roy Conli said "The fact that his character is a robot limits how you can emote, but Scott was hilarious. He took those boundaries and was able to shape the language in a way that makes you feel Baymax’s emotion and sense of humor. Scott was able to relay just how much Baymax cares.
- Daniel Henney as Tadashi Hamada, Hiro's older brother and Baymax's creator. On Hiro and Tadashi's relationship, Conli said "We really wanted them to be brothers first. Tadashi is a smart mentor. He very subtly introduces Hiro to his friends and what they do at San Fransokyo Tech. Once Hiro sees Wasabi, Honey, Go Go and even Fred in action, he realizes that there’s a much bigger world out there that really interests him.
- T. J. Miller as Fred, a laid-back comic-book fan who also plays the mascot at San Fransokyo Institute of Technology. Speaking of Miller, Williams said "He’s a real student of comedy. There are a lot of layers to his performance, so Fred ended up becoming a richer character than anyone expected.
- Jamie Chung as GoGo Tomago, a tough, athletic, adrenaline junkie who is developing electromagnetic wheel axles at San Fransokyo Institute of Technology. Hall said "She’s definitely a woman of few words...We looked at bicycle messengers as inspiration for her character.
- Damon Wayans, Jr. as Wasabi, a smart, slightly neurotic, heavily built neat-freak and an expert on laser cutting at San Fransokyo Institute of Technology. On the character, co-director Chris Williams said "He’s actually the most conservative, cautious—he [sic] the most normal among a group of brazen characters. So he really grounds the movie in the second act and becomes, in a way, the voice of the audience and points out that what they’re doing is crazy.
- Génesis Rodríguez as Honey Lemon, a quirky chemistry whiz at San Fransokyo Institute of Technology. Williams said "She’s a glass-is-half-full kind of person. But she has this mad-scientist quality with a twinkle in her eye—there’s more to Honey than it seems.
- James Cromwell as Professor Robert Callaghan, and the head of a robotics program at San Fransokyo Institute of Technology and Tadashi's professor and mentor, who is then revealed to be the supervillain Yokai.
- John C. Reilly as Wreck-It Ralph, the villain of Fix-It Felix, Jr.
- Sarah Silverman as Vanellope von Schweetz, a racer/glitch in Sugar Rush.
- Jack McBrayer as Fix-It Felix, Jr., the hero of Fix-It Felix, Jr.
- Jane Lynch as Sergeant Tamora Jean Calhoun, the lead character of Hero's Duty.
- Alan Tudyk as King Candy, the ruler of Sugar Rush/Turbo, the former star racer of TurboTime.
- Mindy Kaling as Taffyta Muttonfudge, a racer in Sugar Rush.
- Joe Lo Truglio as Markowski, a soldier from Hero's Duty that Ralph meets in Tapper's.
- Richard Steven Horvitz as Kaos, A renegade Kaos-element Portal Master who is a Minion to Yokai & King Candy/Trubo, he gave away his royal name and fled to the wilderness followed by his butler Glumshanks.
- Lex Lang as Doctor Neo Periwinkle Cortex, Cortex is depicted as a mad scientist who seeks to achieve world domination as an act of vengeance for the ridicule he has suffered in the past. Hoping to achieve this by mutating the local animals into his soldiers, he eventually creates Crash Bandicoot, the titular character of the series, but soon rejects him as unworthy of being in his army and removes him from his castle.
- Roger Craig Smith as Sonic
- Colleen Villard as Tails
- Cindy Robinson as Amy
- Travis Willingham as Knuckles
- Nika Futterman as Sticks
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