Here it is, the 10th feature film from Pixar Animation Studios, and the 10th one to redefine the rules of animated moviemaking, even compared to previous Pixar films. The studio’s last offering, “WALL-E,” worked hard to establish the realistic, nuts-and-bolts details of futuristic mechanical devices, and created a plausible vision of the future in the process. “Up” looks at reality and says, “Eh, who needs it?” A man lifting his house off the ground with nothing more than a thousand helium-filled party balloons? Sure! Dogs with computerized collars that vocalize their thoughts? Why not!

“Up” is an old-school adventure fantasy, complete with biplanes and a zeppelin, offbeat explorers, and exotically dangerous locales. If it were a live-action film, it would be separated into 10-minute chunks and shown as a serial on Saturday afternoons at the local movie house. (In the 1930s, of course. Not today.) It’s breezy, clever, hilarious, and entertaining — all par for the course at Pixar — and has the depth and intelligence that separate Pixar from every other animation factory. Some other cartoons might be funnier, but none have more heart — more genuine, poignant human emotion — than the stories that Pixar tells.

The film is split into two chunks (or, if you prefer, it’s one chunk preceded by a lengthy prologue). In the beginning, there is Carl Fredricksen (voice of Jeremy Leary), a young boy in huge, square eyeglasses who goes to the movies every week to watch films like “Up” — it’s the late 1930s, or thereabouts — and catch newsreels detailing the latest exploits of his hero, the famed explorer Charles Muntz (Christopher Plummer). Carl longs to be an adventurer himself, and is gobsmacked to meet a girl his age, Ellie (Elie Docter), who is similarly inclined.

As Michael Giacchino’s wistful score provides musical accompaniment, we see a wordless montage of Carl and Ellie’s life together: They grow up, they get married, they buy a fixer-upper, they dream of taking an adventure trip to South America, their lives pass happily. Not yet convinced of Pixar’s storytelling brilliance? This sequence conveys that Carl and Ellie wanted children but were unable to conceive — an important part of Carl’s development as a character, but seemingly impossible to relate in a cartoon without being awkward or embarrassing, and yet director Pete Docter (“Monsters, Inc.”) and his co-writer, Bob Peterson (“Finding Nemo”), have done it, as sublimely and beautifully as everything else. What other filmmakers would even TRY such a thing, let alone pull it off with such aplomb?

The meat of the story comes after this prologue, when Carl (now voiced by Edward Asner) is a cranky old widower who misses his departed Ellie and only wants to be left alone. A brief but serious turn of events might lead to his being forced into a retirement home, and so, left with no alternative, he affixes a thousand helium balloons to his house and floats away. His destination: Paradise Falls, in South America, where he and Ellie always wanted to go.

As you probably already know, however, Carl is not alone. Russell (Jordan Nagai), a relentlessly helpful neighborhood boy and Wilderness Explorer, was under the porch when the house lifted off, and is now along for the ride whether Carl likes it or not. (Spoiler: Carl does not like it.) What follows is a story that grows broader and crazier as it goes, with Carl and Russell reaching South America and encountering unusual animals and a deranged human, before it finds its way back to sanity again in time for a sweet, satisfying conclusion.

The film is hard to classify by genre. It has elements of the road-trip odd-couple buddy comedy, and some dazzling adventure (the vertiginous heights attained by the balloon-house are particularly impressive in 3D), with some ruminations on mortality and the importance of seizing the present rather than dwelling on the past. The story is often very funny but seldom wacky or slapstick, and it’s bookended by sequences that are something else altogether: touching and heartfelt, and unlike almost anything I’ve ever seen in an animated film.

There are details in the middle part of the story that seem daffier and less plausible than they ought to be, though that might just be a personal preference. (Don’t you hate when movie critics say “they shouldn’t have done that” when all they really mean is “that’s not how I would have done it”?) At any rate, despite the story’s high-flying extremes, the characters and their emotions are consistently grounded in reality. Pixar has once again made a movie full of vivid imagination and whimsy, a genuine treat for kids and grownups alike.

A- (1 hr., 38 min.; PG, mild action violence and dangerous situations.)