Let’s begin with this: don’t leave early.  Stay all the way through the credits for the final scene, which establishes the movie’s Marvel bona fides.

And this: don’t arrive late, for the lead-in animated short, Feast, is all heart and pure genius, nearly worth the price of admission in itself.

And this: where can I get an inflatable personal health-care companion for myself?

Disney’s Big Hero 6 is loosely based on a little-known Marvel comic of the same name.  The story plays out against the beautifully imagined city of San Fransokyo.  The central character is a 14-year-old orphan named Hiro Hamada (Ryan Potter), a budding tech genius who’s already graduated from high school.  His older brother, Tadashi (Daniel Henney), wants to convince Hiro to stop wasting his talents on back-alley bot-fighting and join the exclusive technology institute where he is a student.  There, Hiro meets Tadashi’s friends, enthusiastic young inventors with improbable names like GoGo (Jamie Chung), Honey Lemon (Genesis Rodriguez), and Wasabi (Damon Wayans Jr.) — and oh, yes, their friend Fred (T. J. Miller), who knows nothing about science but dreams of being a Godzilla-like superhero.

Hiro earns a spot in the academy with a public exhibition of his new robotics invention.  But later, when a fire breaks out, Tadashi rushes back in to save his beloved professor Callaghan (James Cromwell) and perishes in the attempt.  The grief-stricken Hiro is then cared for by Baymax (Scott Adsit), a tubby, inflatable “personal health-care companion” invented by Tadashi.

Baymax, in his robotic innocence, comes across as sweet and solicitous; when his scanners tell him that Hiro is upset, he prescribes hugs and being with friends.  But Hiro discovers that some mysterious villain in a kabuki mask has stolen his robotics, and suspects that the fire that killed his brother was no accident.  He outfits the peaceful Baymax with fighting gear and programs him for karate, then creates superhero identities for GoGo and the rest, based on their own inventions.  And Fred?  He gets to jump around in a ridiculous looking dragon suit, breathing fire — an anime fanboy’s dream come true.

The somewhat thin plot turns, of course, on finding the identity of the man in the mask and bringing him to justice.  Along the way, Hiro has to wrestle with his conscience and lust for revenge.  The rest of the team provides both the humor and the action needed for a Disneyfied superhero flick (and, one assumes, plenty of opportunities for marketing action figures, just in time for Christmas).

The emotional heart of the film, however, is the interaction between Hiro and Baymax.  Not surprisingly, some of the humor depends on underwear jokes and references to flatulence (as did last year’s Cloudy with a Chance of Meatballs 2).  But the script digs deeper, as the robot’s pre-programmed single-mindedness becomes the foil for Hiro’s adolescent struggles with feelings of loss, dependence, and friendship (and here, I’m reminded a bit of 2012’s Robot & Frank).  Indeed, parents with more sensitive youngsters should watch their children’s reactions and be ready to talk with them about the story.

As with many movies written for a younger demographic, the adults in the film are largely accessories, providing either villainy or comic relief.  But Baymax himself, somewhat featureless and generic, makes a nice pseudo-parental projection screen for our ideas of love and sacrifice.  Those whose job it is to care for others must sometimes make heroic sacrifices to get the job done.  Knowing and appreciating the care we have received, we are better equipped to care for others.

Even without high-tech superpowers.