Filled with the spirit of adventure and a lot of heart, Up, the unlikely tale of an old man and a little boy who sail to South America in a house pulled aloft by thousands of helium balloons, is so far the best film of the year. And anything coming down the pipeline between now and December will be hard pressed to top it.

The latest film from Disney’s Pixar Studios, which has given us the likes of WALL•E, Ratatouille, Finding Nemo and the Toy Story movies, recently became the first animated film to open the Cannes Film Festival in its 62-year history. (It’s also the first animated film to feature a miscarriage and the death of a beloved character in the first reel, but don’t let that dissuade you.)

It’s a character-driven film whose wordless opening sequence chronicles a lifelong love affair that resonates through the rest of Up, adding more than a little sentimentality and melancholy emotion to everything that follows. It’s what takes Up way beyond what could have been merely a grand adventure tale that sends crotchety 78-year-old Carl Fredricksen (voice by Edward Asner in grumpy old-men style) and his 10-year-old accidental stowaway Russell (the buoyantly cheerful Jordan Nagai) on a skyward flight in a two-story house bound for Paradise Falls somewhere in remotest Venezuela.

Up, however, opens in the 1930s when little Carl, thrilled by the exploits of adventurer Charles Muntz (Christopher Plummer), meets a like-minded little girl named Ellie. They are devastated when paleontologists dismiss Muntz’s claims of having found the skeleton of an enormous, big-beaked bird. Soon after, the disgraced Muntz disappears into the wilds of South America in hopes of proving his claim.

Meanwhile Carl and the irrepressible Ellie, whose dream it is to get to Paradise Falls, find themselves on the same wavelength and become inseparable.

A wistful montage chronicles their relationship through good times and bad. Carl’s coin jar, in which he’s saving for the trip to Paradise Falls, continually is smashed to pay for things such as a new car or upkeep on the house. As Carl and Ellie grow old, this beautifully done wordless sequence becomes increasingly sentimental, yet honest. Nothing is spared.

Carl, who sells balloons in a park, has not forgotten Ellie’s dream, however. And when it comes time to be shipped off to a retirement home, he rebels by tying thousands of balloons to the roof of his house in hopes of taking it to South America.

What Carl didn’t count on, however, is that chubby little Russell, who has been pestering Carl with offers of help so he could get his “assisting the elderly badge” in the Wilderness Explorers troop, would be on the front porch when the house went aloft.

What follows are a series of increasingly wonderful and wacky adventures –– everything from the terrors faced when the house is tossed back and forth in a lightning storm that rivals the tornado in The Wizard of Oz, to a pack of angry talking dogs, to the discovery of the real-life giant bird, that Russell names “Kevin,” to an even more monumental discovery in the jungle near Paradise Falls.

Yet no matter what calamities befall the hapless Carl, he remains true to Ellie’s ideals.

Director Pete Docter (Monsters, Inc.) and writer/codirector Bob Peterson have made Ellie such a solid figure in Up’s opening sequence that she is a very real presence throughout the entire film, symbolized by the house she loved.

What makes the film special, too, are all the little throwaway bits and sights that delight — the pack of dogs ready to leap into action at the word “squirrel!” or salivating at the word “treat” or playing poker using dog biscuits for chips.

Kevin, a giant bird that has blue, red and yellow iridescent feathers and an enormous red beak, is what the dogs are after at the behest of their mysterious master. They are determined to bring the bird back dead or alive.

The dogs’ thoughts have been given voice via the collars they wear. They refer to Russell, dressed in his Wilderness Explorers uniform, as the “small mailman.” The collars provide offbeat moments, particularly when the collar of the lead alpha dog — a Doberman — goes haywire and he begins speaking in a funny, high-pitched voice.

When Kevin persuades the reluctant Carl to help Kevin get back home, they find unexpected help from one of the dogs, a floppy canine named Dug who wants to join the rest of the cliquish pack but is considered less than second-rate by them. Dug (voiced by screenwriter Peterson) adds a much-needed sense of heart, heroism and fallibility to the latter part of Up which otherwise might have drifted into just another extended chase sequence.

See it in 3-D if you get the chance. The colors are not as bright as they are in the 2-D version, but the seamless 3-D effects are sometimes breathtaking, especially when the characters are hanging over a void clinging to a garden hose attached to the house.

There is heroism in the film, and lots of surprises.

Even for Russell, a city kid in the Wilderness Explorers troop, who looks around at all the troubles he and Carl have encountered and decides that the wilderness isn’t all it has been cracked up to be in the books he’s read. It’s “kind of wild,” he says. So is Up, which is also kind of wonderful.

*****Up

Voices: Edward Asner, Christopher Plummer, Jordan Nagai, John Ratzenberger, Delroy Lindo.

Rated: PG, contains cartoon violence.

mjanuson@projo.com