It has been just over a decade since Bob Iger engineered the deal that brought Steve Jobs’ Pixar Animation Studios to Disney, negotiating a $7.4 billion stock purchase that raised eyebrows at the time. But it swiftly proved to be the smartest move of Iger’s career, restoring his company to the height of the Disney Renaissance — that period from 1989 to 1999 that resulted in classic cartoons such as “The Little Mermaid,” “Beauty and the Beast,” “Aladdin,” and “The Lion King.”

Pixar’s “Finding Dory” and Disney’s “Zootopia” are this year’s second- and third-highest-grossing films, and Disney’s “Frozen,” from 2013, holds the all-time record, with $1.3 billion in global receipts.

The Pixar deal went a long way toward appeasing Walt Disney’s nephew, Roy E. Disney, whose concern that the company had de-emphasized animation helped lead to Michael Eisner’s 2004 ouster. And by putting Pixar chief creative officer John Lasseter and president Ed Catmull in charge of Walt Disney Animation Studios, Iger bet on the two visionaries who had revolutionized the business with their unprecedented track record of success.

But the formula that worked at Pixar wasn’t going to apply at Disney, Lasseter and Catmull soon realized. At the time, Disney’s animation division was suffering from a creative identity crisis, management issues, and morale problems. Lasseter tells the story of a disillusioned Disney artist he met soon after the merger, who said, “You don’t know what it’s like to work for four years, put your heart and soul into a film, and the day the film opens, no one mentions it again.” The encounter broke Lasseter’s heart and served to illustrate the vast differences between Pixar’s and Disney’s working cultures.

“The way we saw ourselves at Pixar, we were a filmmaker-driven studio,” says Lasseter. “What developed in that second heyday of animation under [Jeffrey] Katzenberg was an executive-led studio.”

From the head of the studio to the development team, the “suits” felt compelled to offer notes on each project that the directors were obligated to incorporate. “No longer were they focused on trying to make the best movie. They were negotiating notes,” Lasseter says.

The new animation bosses turned the reins back over to the filmmakers, but the teams remained fundamentally different: At Pixar, movies are typically directed by one person, nearly always one of the original “brain trust” (Lasseter, Pete Docter, Andrew Stanton, Joe Ranft); by contrast, Disney tends to produce two-director projects.

“It’s just a different heritage,” Catmull explains.

After the merger, the new management was determined to keep Pixar and Disney separate, mostly for Disney’s sake. “If it was felt that Pixar’s production team had bailed them out, it wouldn’t be Disney’s victory,” Catmull says.

But the idea of separate fiefdoms was challenged almost immediately on a Disney project called “American Dog,” which became “Bolt.” The film faced big changes late in the game, and the Disney team insisted it couldn’t make deadline. But Lasseter and Catmull refused to use Pixar resources, and what appeared to be a crisis was resolved by creative solutions.

“When they finished the movie, it was theirs,” says Catmull.

According to Lasseter, the philosophy of a “brain trust” — redubbed “story trust” at Disney — was the only thing imported from Pixar. As a project develops, the filmmakers pitch their progress to their peers, and anyone — from Lasseter to a mailroom employee — can suggest changes. Then, it’s up to the director to decide whether or not to act on them.

In 2014, Disney promoted Jim Morris and Andrew Millstein to president of Pixar and Walt Disney Animation, respectively. They handle day-to-day affairs, freeing up Catmull to focus on advising and motivating the next generation.

“The people who are here feel like they own the studio,” Catmull notes.

One reason for Disney’s transition from executive-driven studio to a collaboration of creatives is that Lasseter knows how it feels not to be heard. He had been through the Disney apparatus before, starting his career there after graduating from Cal Arts in 1979. It was a stagnant time in the studio’s history, as the last of Disney’s Nine Old Men (animators such as Frank Thomas and Ollie Johnston) were finishing out their careers.

“Frank and Ollie told me that when Walt died [in 1966], there was a lot of discussion about closing Disney animation,” recalls Lasseter, who, two decades later, was doing tests with computer-animated backgrounds for a possible “Where the Wild Things Are” project. As Lasseter tells it, Walt Disney himself was a major believer in technical innovation. “The whole purpose was to make animation more believable to the audience. The multiplane camera is a great example,” he says. “When I saw computer animation, I said, ‘This is what Walt would have done.’ It was as plain as the nose on my face.”

But his supervisors at Disney were less visionary, focused on working cheaper and faster, so Lasseter was shown the door — and went off to prove them wrong at Pixar, where “Toy Story” revolutionized the industry in 1995.

Whereas Pixar was founded by animators committed to working with digital tools, the Disney team had a hand-drawn tradition. “There was this fear that the artistry would get lost in the transition to technology,” recalls “Zootopia” co-director Byron Howard, who has been with the studio since “Pocahontas” — and who switched to the story department, “so I could keep drawing.”

Ironically, when Lasseter took charge at Disney Animation, one of his goals was to revive the studio’s hand-drawn (or 2D) animation efforts — a strategy that yielded “The Princess and the Frog” and a “Winnie the Pooh” reboot. But both films were box office disappointments.

“I was determined to bring back [hand-drawn animation] because I felt it was such a heritage of the Disney studio, and I love the art form,” Lasseter says. “I was stunned that ‘Princess’ didn’t do better. We dug into it and did a lot of research and focus groups. It was viewed as old-fashioned by the audience.”

The hand-drawn tradition isn’t dead altogether; rather, it has been incorporated into Disney’s new computer-empowered style — as in the Nov. 23 release “Moana.” For instance, the tattoo on demigod Maui’s chest was animated using 2D techniques. The film marks the CG debut of “The Little Mermaid” directors John Musker and Ron Clements.

These days, it isn’t always easy to tell a Disney project from a Pixar movie, notes “Frozen” and “Frozen 2” director Jennifer Lee. “Brave,” the 2012 princess-driven fairy tale, “breaks your idea of what a Pixar movie is,” she says, “while ‘Zootopia’ — I could see either studio making it.”

Lee says she’s awed by the unconventional thinking behind some upcoming Disney projects. The philosophy, she says, is, “Don’t get complacent.” She cites the example of “Frozen 2,” noting, “There’s never been an animated theatrical release of a musical sequel. We’re scared.” And that’s a good thing.