Continuity mistake: When Hiro stubs his toe and Baymax wakes up his charging station is in Tadashi's space. When they get back from the police station on the same day it is plugged in on Hiro's side.
Other mistake: In the scene that Callaghan's daughter went into the portal, there is a track for the capsule to go into the first portal, but there was no track for the return portal.
Continuity mistake: In the scene at the college where Callaghan asks to look at Hiro's Megabot, Callaghan's shirt is blue, but when he holds out his arm to take Megabot, his shirt sleeve is red. Later on he is wearing a red shirt at the SFTT. (00:13:30)
Continuity mistake: When Honey meets Hiro, she has earbuds in her ears playing music. She starts talking to Hiro, pulls them out of her ears, and they dangle out of her shirt. The dangling earbuds disappear in the close up shot of her and Hiro.
Factual error: When the car goes to the bottom of the ocean after the chase, the water in it is raising as if leaking in, despite the fact that the door on Hiro's side is missing and the water should be rushing in. (00:50:15)
Suggested correction: I watched the scene and it looks like it's filling up the way it should. It's looks similar to the way a car fills up after being submerged with the windows open.
Not true, water is still filling up the car way too slow for an opening like this. The car should be filled up immediately.
You're wrong thinking it would fill up immediately. But even so, it fills up in about 10 seconds (even less if the shot of it filling up is meant to be a simultaneous shot and not continuous).
Other mistake: Honey touches the pink ball and it explodes into a pink puff of smoke. Despite standing in the smoke with Honey, Hiro does not get any of the pink on him, whereas Honey is covered in it.
Character mistake: Baymax, a healthcare robot, says that his programming includes a database of 10,000 symptoms of disease. Yet, he issues the warning, "After eating, wait one hour before swimming." That warning, often given by parents to their children, has no basis in medical fact. People who do not get cramps after eating will not develop cramps by going swimming after eating: http://www.snopes.com/oldwives/hourwait.asp.
Other mistake: To save the two from the portal, Baymax overrode his healthcare protocol by removing the chip and placing it in his glove. However, he still asked whether Hiro was satisfied with his care before shutting down.
Suggested correction: He says it before the moment when camera not looking at him for a second, when he had a chance to remove the chip.
Audio problem: When Aunt Cass offers to make wings, the voice actor says, "with the hot sauce that makes our faces melt", but the animation reflects, "with the hot sauce that melts our faces off."
Continuity mistake: When Hiro and Baymax are in the warehouse the single microbot is let go by Hiro before they are attacked, linking with the others. A few minutes later, the microbot is seen back in the Petri dish again before they are attacked.
Suggested correction: Microbot was always in Hiro's pocket and never joined others.
Other mistake: In the garage when completing his invention there are 12 blue bins full. But only 5 characters have a bin each entering the building, but there are 6 bins when they are chatting before the inverters show. (00:16:29)
Continuity mistake: At the end, Baymax rocket-glove changes model. When Baymax puts his Rocket-glove at the thruster on the ship it has the original model seen earlier in the movie, however, when the ship exits the space through the portal and the glow shuts-down it has another model. (01:27:00 - 01:29:00)