Last year's battle between Pixar and DreamWorks for the family animated movie demonstrated the clear distinction between how the two of them go about their work. DreamWorks gave us the bright Kung Fu Panda, a film chock-full of big name voice talent, names that the studio then made a hearty part of the advertising campaign. Pixar gave itself, however, a much harder sell with the far riskier Wall-E, a film that for 40 minutes at least was jaw-droppingly strong, before turning into a more conventional kids' movie.

Both films were very good. Both made a lot of money. But they demonstrated that if you want the more daring film, it's Pixar all the way.

But could it have bitten off more than it can chew this time around? Because this summer, Pixar releases Up into the world, arguably its biggest risk to date. That's because this is the only major, big budget movie that we can remember that puts a 78-year old grumpy man as its central character. Focus purely in on the family animated sector, and we'd be surprised if it's ever happened before. And if it'll ever happen again.

If you're not familiar with Up, then the man in question is Carl Fredericksen, a widower who keeps his promise to explore mountains to his late wife with the help of a boatload of balloons tied to his house. It looks a little Roald Dahl-inspired to us, and joining him on his adventure is an overweight 8-year-old.

Be honest: it's not the kind of stuff you expect to find on the shelves of the Disney Store, is it?

And that's part of the problem that Pixar is said to be facing. The lucrative merchandise market is what turned Cars - whose box office performance was good, but some way off Finding Nemo levels - into one of the most lucrative cash cows that Pixar has ever produced. Cars merchandise currently holds the record for Pixar, bringing in a staggering $5bn of revenue, far in excess of the film's box office and DVD sales (almost inevitably, Cars 2 is on the way). But that's not going to happen this time round. In fact, many seem to be worried about what's going to happen instead.

Firstly, there's a belief that Up isn't going to be the stellar performer that Pixar films usually are. While the Pixar brand will no doubt put an assortment of bums on seats, it's nonetheless going to be a tough sell to a family audience, who are far more comfortable with kids' movies about animals, spaceships, fast cars and toys. Up seems to have none of them. Pixar's last two films, Ratatouille and Wall-E, weren't easy sells either, and some are pointing to the fact that those two - while still making lots of cash - were the worst performers in recent times for the firm. Up, they suspect, is going to struggle to match them.

Various business and research experts have weighed in with their thoughts. As reported in the New York Times, Doug Creutz of Wall Street's Cowen and Company said "The worries keep coming despite Pixar's track record, because each film it delivers seems to be less commercial than the last." Even the argument that Pixar has never had a flop doesn't seem to cut the mustard.

And then there's Pali Research's Richard Greenfield, who arguably gets to the nub of the problem: "We doubt younger boys will be that excited by the main character." Off the back of his words, Pali Research then downgraded Disney shares to sell, with the expected underwhlelming box office performance of Up one of the main contributory factors to that decision.

The problems mount with the aforementioned merchandise. Over in the States, Wal-Mart and Target have already confirmed that they won't be taking very much in the way of Up merchandise, simply because the manufacturers themselves aren't very enthused by it. And it was reported a week or two back that Thinkway Toys, a firm that has been producing Pixar movie tie-in merchandise since the Toy Story days, won't be making a single Up related item.

No matter how well the film does at the box office - and that's, despite Pixar's track record, not to be taken for granted this time round - the lack of merchandising revenue is going to hurt. Just ask the main Disney company, which in the 1990s followed up The Lion King a few years later with The Hunchback Of Notre Dame, and saw merchandising revenues tumble as a result.

Disney and Pixar, meanwhile, are being bullish, and perhaps rightly so. The upcoming slate has two banker sequels in the next two years, namely Toy Story 3 and Cars 2. Plus there seems to be an excitement about the film amongst those who have been treated to much from it. It'll be at the Cannes Film Festival next month, and how often has that happened where supposedly mainstream American animated movies are concerned? As Disney Chief Executive Robert Iger said, "We seek to make great films first. If a great film gives birth to a franchise, we are the first company to leverage such success. A check-the-boxes approach to creativity is more likely to result in blandness and failure". He's certainly saying the right words, but will all concerned by holding their nerve once the numbers come in?

For the problem Up faces is that the wrong people seem to be getting excited about the film. Given that Pixar has invested around $200m in the movie, it has little choice but to target a mass market family audience to bring that money back in. And the truth is that it's set itself its hardest sell to date, with a film that could possibly find itself astounding critics (again), but leaving the people who Pixar is relying on to recoup its investment cold.

We find ourselves desperately hoping it succeeds, given that Pixar seems to be taking more cold, hard risks than any other major studio out there. It's already proven that it can sell something like Wall-E to a mass audience, even though it may not have come anywhere near those Finding Nemo-like numbers. But can it sell Up, too?

The answers start coming in from the end of May, when the film commences its worldwide rollout. And we do suspect that one way or another, Pixar won't be having too many regrets about making Up. Yet should it be the first of its projects to burn at the box office - and despite what some of the experts say, that's no certainty - we just hope it doesn't throw the firm off its course. After all, we like Kung Fu Panda. But we like Wall-E a whole lot more...