IT has been a cinematic partnerships to rival Laurel and Hardy, Fred and Ginger, Yoda and Vader. But like many a Hollywood double act, the off-screen relationship between Walt Disney and Pixar has been fiery, full of jealousies and perceived slights. Both sides are working hard to keep things together but in the next month it could all be over — and both sides have much to lose.

In six computer-animated films Pixar has created a universe of characters to sit alongside Disney’s classics. Since 1995, when Pixar and Disney released their first joint venture, Toy Story, the high-tech studio has seemed unable to put a foot wrong.

Toy Story, A Bug’s Life, Monsters Inc, Toy Story 2, Finding Nemo, The Incredibles — each successive Pixar film has earned more money in a record run that, film for film, makes Pixar one the most successful studios of all time.

But by Christmas, as children around the world open Pixar products from Toy Story pyjamas to Nemo DVDs, the partnership could be over, at least as far as Disney is concerned.

Apple computers mogul and Pixar chairman Steve Jobs has repeatedly threatened to end the partnership after falling out with Disney’s former boss, Michael Eisner. Last week he said Christmas was the deadline.

Until recently the Apple boss had held all the trump cards. Pixar’s record-breaking run of hits coincided with years of disappointment for Disney’s own animation studio. Now Disney is back with a hit of its own — Chicken Little.

The film is the first of a series of computer-animated films from a reinvigorated Disney animation department. There had been speculation in Hollywood that this time the sky really would fall in on Chicken Little. The film got a so-so reception at a recent industry screening, but it opened this month to $40m (£23m) in its first weekend — a more than respectable debut.

Not that Pixar has been left lagging behind. The studio has no new release this year but last week Jobs announced quarterly net income was up 22%, fuelled by profits from Pixar’s growing film library.

Relations between Disney and Pixar have warmed since Eisner made way for Bob Iger, his former deputy, In September. But problems remain. Last week Jobs said he was having “deep discussions” with Disney. “Our discussions right now are very productive,” he said. “That’s where we are today.”

It is where they have been, on and off, for almost two years in fact. In the next few weeks both sides will finally decide whether to patch things up or move on. As so often with marital difficulties, the root of their problems lies deep in their past.

Pixar was originally the computer-animation division of the company run by George Lucas, creator of Star Wars. Tech- savvy Jobs bought it in 1986 for $10m (it is now a public company valued at $6.7 billion) hoping Hollywood would like Pixar’s new form of 3D animation. Disney, for so long an innovator and leader in animation, seemed a natural ally.

Their first joint venture was Toy Story, financed by Disney and overseen by Pixar’s creative guru John Lasseter. At the time it must have seemed like a gamble and Disney negotiated 87% of the proceeds, including its distribution fee.

Toy Story proved to be the sort of financial and critical success Disney had not seen in years. It also sounded the death knell for Disney’s traditional, hand-drawn cartoon features.

In the year of its release, Toy Story made $362m worldwide and went on to be a merchandising success for Disney to rival only Winnie the Pooh and Mickey Mouse.

In 1997 Jobs and then Eisner hammered out a deal for five more animated features. Pixar retained full creative control and equal billing while Disney was in charge of the distribution, marketing and licensing.

The new deal was a 50-50 split. Pixar paid half the cost of developing and producing the movies in return for half the cash from all sources, except theme parks, after Disney deducted its costs and took its 12.5% distribution fee.

Jobs also handed over the sequel rights to Pixar’s creations, an agreement that was eventually to undermine his relationship with Eisner and ultimately perhaps Disney.

The two men began to clash in private and later in public. Pixar went on to provide hit after hit for Disney, each bigger than the last. At the same time Disney’s creative juices seemed to dry up. In 2002 Disney released Treasure Planet, which cost $140m to make, took less than $17m in its first weekend and died. Pixar’s Monsters Inc, released a year earlier, took $100m in its first nine days and went on to create hit toys and best-selling DVDs.

The hits contributed to Jobs’s feeling that he was being hard done by. Many shareholders felt the same way and pressure mounted for Eisner to step aside.

In a series of ever more fractious meetings Jobs and Eisner failed to reach an agreement. The sequel option seems to have been the biggest obstacle. And in January 2004, the year Finding Nemo became the best- selling DVD of all time, Pixar announced that it would terminate its deal with Disney after delivering its fifth and final movie, Cars, in 2006.

According to the author of DisneyWars, James Stewart, Jobs told Roy Disney, nephew of the company’s founder, he could “never make a deal as long as Michael Eisner is there”.

Almost two years on, life has changed dramatically at Disney. Eisner has gone and Disney has an animation hit of its own, and a slate of computer- animated films to follow. They may never match Nemo, but Chicken Little’s success marks a significant shift in the right direction for Disney.

Perhaps more tellingly, Jobs appears to have found that getting a new partner is easier said than done. Some studio executives say that, again, sequels are the sticking point.

If Disney and Pixar divorce, Disney gets the house. In the next few weeks Jobs must decide if he is really ready to leave.