Summer means one thing in Hollywood: big, blockbuster movies. But a single superhero film has ka-powed all others this year.

The Avengers, from Walt Disney’s Marvel unit, stormed the box office, bringing Iron Man, the Incredible Hulk and Thor together in the top grossing release with close to $1.5bn in global ticket sales.

The film is now the third-highest grossing title of all time, behind Avatar and Titanic. Its success has largely validated Disney’s $4bn purchase of Marvel in 2009.

The acquisition was not only about movies: Disney plans to use Marvel’s vast library of superhero characters in every part of its business from theme parks to television shows and consumer products, adding Incredible Hulk underpants and Iron Man lunch boxes to Disney’s staple inventory of Mickey Mouse merchandise.

But the Marvel deal has also added some dramatic tension to the family-oriented company based in Burbank, California – largely, it appears, because of the management style of Isaac “Ike” Perlmutter, Marvel’s chief executive.

From his home in Florida, Mr Perlmutter runs Marvel as a division within Disney. The 69-year-old’s influence and particularly his interest in merchandising and toy licensing has shaken things up throughout Disney’s consumer products division.

In the past year Andy Mooney, chairman of the unit, has left. Several lieutenants followed, including three female executives who hired a lawyer to seek individual financial settlements.

Separately, another senior female executive filed an internal complaint about Mr Perlmutter, alleging that he made threatening remarks to her. The woman eventually changed jobs at Disney.

A spokesperson for Disney declined to comment, citing privacy on personnel matters. Mr Perlmutter also declined to comment on the situation.

Mr Perlmutter was Marvel’s largest shareholder before Disney bought it and he took much of his $1.5bn payment in Disney shares, giving him a seat at the decision-making table.

He is Disney’s second-largest individual shareholder behind the Steve Jobs Trust, with 25m shares – equivalent to less than 3 per cent of the company. Since the deal, his Disney shares have increased in value by about 50 per cent to around $50.

Over the past three years, he has become a force within Disney. But his strong opinions and skill as a cost-cutter often put him at odds with colleagues.

In a series of interviews, the Financial Times has tracked the transition at the lucrative products unit and subsequent upheaval among its staff.

“Usually when a company takes over another its culture is the one that prevails,” says one of these people. “But in this case it was the other way round.”

Disney Consumer Products, commonly called DCP, is smaller than Disney’s theme park, media networks or movie studio divisions but is highly profitable.

In the 2011 fiscal year, it generated operating income of $816m – about 10 per cent of all Disney profits that year – on revenues of $3bn. In Disney’s most recent quarterly earnings report, DCP operating income was up 35 per cent to $209m.

Mr Mooney was the head of DCP who oversaw the creation of the Princess line of toys, books and other products, which generates $4bn in retail sales every year. The Scottish former chief marketing officer at Nike, Mr Mooney was hired by Disney in 2000.

In February 2011, Mr Mooney was a featured speaker at an investors conference at the Grand Californian Hotel in Anaheim where he outlined his vision for “active licensing” by Disney – his term for pursuing long-term deals with licensees that can often yield profitable new products.

By September, the 57-year-old was gone, his ambitions cut short by repeated conflicts with Mr Perlmutter, according to people familiar with the situation. The two sparred over the direction of DCP. Mr Mooney wanted to continue to nurture long-term relationships with toy and other licensees; Mr Perlmutter argued for shorter-term deals with large minimum guarantees. Mr Mooney declined repeated requests to comment.

Unlikely mogul who saw potential in Marvel characters Ike Perlmutter has always been one of Hollywood’s unlikelier moguls, writes Matthew Garrahan. Born in Israel, he served in the army in the Six Day War of 1967 before coming to New York. He earned money early on by standing outside Jewish cemeteries in Brooklyn and offering to lead burial services in Hebrew. He was adept at the art of the deal, friends say, and was soon selling toys and beauty products in Manhattan. He taught himself to read a balance sheet and formed Odd Lot Trading Co, a retailer and wholesaler of discontinued items. He sold it in exchange for a stake in Revco, a chain of drug stores. By the early 1990s he and Avi Arad, a fellow Israeli, had bought a toy company that depended heavily on Marvel characters. When Marvel declared bankruptcy, the two men grasped its potential and won a takeover battle against two tough corporate raiders: Carl Icahn and Ron Perelman. Realising that films could drive toy sales, Mr Arad and Mr Perlmutter struck deals between Marvel and Sony Pictures and 20th Century Fox, creating hits with the Spider-Man and X-Men movies.

A battle of loyalties flared in the division, where some senior staff had qualified for bonuses in 2011 because of the unit’s financial performance. Anne Gates, the chief financial officer of DCP, and Jessica Dunne, head of global product licensing, had run-ins with Mr Perlmutter that were observed by other staff.

Ms Gates and Mr Perlmutter clashed over how she compiled financial reports. Mr Perlmutter wanted her to use Marvel’s format for spreadsheets, say two people familiar with the matter. “She got verbally abused,” says a person with knowledge of the encounter.

Ms Dunne later filed a written complaint about Mr Perlmutter regarding a disagreement over an email she sent. Ms Dunne told colleagues she was frightened because Mr Perlmutter, in a rebuke, had allegedly said that he had a “bullet with [her] name on it”, according to several people familiar with the matter.

“Everyone encouraged her to file a complaint because she was genuinely concerned for her safety,” says a former colleague. Ms Dunne declined to comment.

A racial remark allegedly made by Mr Perlmutter to Mr Mooney was also relayed to senior Disney managers, the FT was told by people familiar with the account. Mr Perlmutter is said to have detailed efforts to cut costs at Marvel, including a switch in actors in the sequel to Iron Man.

The first movie featured an African-American actor, Terrence Howard, as Colonel Jim Rhodes. Don Cheadle, another African-American actor, was hired for the same part in the sequel at a cheaper price.

Mr Perlmutter apparently told Mr Mooney the change cut costs. He allegedly added words to the effect that no one would notice because black people “look the same”.

Disney and Mr Perlmutter declined to comment on the allegations. A person close to Mr Perlmutter disputed the account.

Separately, a Marvel spokesperson said in a statement: “Mr Perlmutter and all of Marvel have a long record of diversity in the workplace and on movie sets around the world as evidenced by both Mr Perlmutter’s own history and Marvel’s management team.”

People who filed statements with Disney’s human resources department say managers were cautious about the claims.

“They just said they would talk to Ike and tell him to watch how he talked to people,” says one person with knowledge of the investigation. “People at Marvel were used to it but people at Disney weren’t.”

Vanity reigns supreme in Hollywood but Mr Perlmutter has always guarded his privacy assiduously. No public photographs exist of him and he spends most of the year at his home in Palm Beach, Florida.

On a rare visit to Hollywood, for the 2008 premiere of Iron Man, he attended in disguise. “He walked right past me and I had no idea it was him,” says one person who saw him that night.

He can be just as obsessive about saving money – even on stationery. “He used to do this thing in our office that people would laugh at,” Avi Arad, a movie producer and longtime associate of Mr Perlmutter, told the FT in 2009, shortly after Disney’s purchase of Marvel. “If there was some used paper or a memo lying around he would rip it into eight pieces and he would have a new memo pad.”

Mr Perlmutter’s ability to gain a big bang for each buck appealed to Disney. “One of the main reasons Disney bought Marvel was because it could make a great looking movie for a fraction of the price of a Jerry Bruckheimer movie,” says one industry executive, referring to the Pirates of the Caribbean producer who has had a long-term relationship with Disney.

Mr Perlmutter’s hard-driving approach has won him admirers, including Stan Lee, who created some of Marvel’s most popular characters, such as Iron Man and the X-Men.

“I have the greatest respect for him,” Mr Lee told the FT at a recent Comic-Con convention in San Diego. “He doesn’t look for publicity and he keeps himself to himself.” Marvel, Mr Lee added, “is run so beautifully . . . Ike is to a large part responsible for that”.

On paper, Marvel and Disney looked a perfect fit. Back in 2009, Disney was rethinking its entire approach to film-making in response to a contracting home entertainment market: DVD sales had fallen across the industry and every studio in Hollywood was under pressure to cut costs.

Disney was ready to move to a franchise-led strategy, producing films and brands that could generate sequels and spin-offs.

It had acquired Pixar, the commercial animation powerhouse behind films such as Toy Story and Finding Nemo, paying $7.4bn in 2006. Marvel was the next piece in the puzzle, a brand that could deliver movies with stories that appealed to teenage boys – a demographic Disney found elusive.

Marvel movies now loom large for Disney over the next two years, with sequels to Thor and Captain America in production and slated for release. A sequel to The Avengers is also in the works. The performance of the first film has wowed analysts.

“At the time, a lot of investors questioned the value of the deal,” says Tuna Amobi, an analyst at Standard & Poor’s. “But with The Avengers, the upside has become clearer and investors are now sold on [Marvel] being a great acquisition.”

Pixar has re-energised Disney’s animation studio but Marvel may turn out to be a better buy, says Mr Amobi. “I would argue that Marvel gives you more upside from an earnings perspective.”

When Mr Mooney left Disney in September 2011, a company release said he “decided to seek a leadership role with another organisation”. The reality was Mr Mooney was pushed after his contract was not renewed by Bob Iger, Disney chief executive. Disney declined to comment but group insiders said the unit was not working well with other divisions.

Mr Mooney was replaced by Bob Chapek, Disney’s former home entertainment head who helped secure Hollywood’s adoption of Blu-ray discs. Mr Chapek offered the top licensing job at DCP – empty since Ms Dunne’s dispute with Mr Perlmutter – to Josh Silverman, a Marvel executive.

Mr Chapek reorganised DCP around Disney’s big TV and film franchises rather than individual product categories, abandoning the structure used by Mr Mooney, says a person close to the company. Many of Mr Mooney’s former colleagues opted out.

Gary Foster, head of communications, left within the year for a job at another company as did Russell Hampton, Disney’s publishing head who was to be relocated from New York to the company’s Burbank headquarters. Susan Garelli, head of HR at DCP, also departed; Jim Fielding, the head of Disney stores, and Vince Klaseus, who ran the toys business, left for new jobs. None responded to requests for comment.

“All of Andy’s direct reports have left,” says a person with knowledge of the situation. Three female executives – all African-Americans – became part of the exodus and have since sought settlements.

Anne Gates, the chief financial officer, left following Mr Chapek’s reorganisation of the division. Pam Lifford, the head of fashion and home products, quit after her unit was closed. Both women were said to have been offered alternative roles with comparable pay in the company. Susan Cole Hill, an executive with DCP’s HR department, left after her role was eliminated following the restructuring. The three women declined to comment.

Ms Gates, Ms Lifford and Ms Cole Hill have hired Dan Stormer, a partner with the Pasadena law firm Hadsell, Stormer, Keeny, Richardson and Rennick, to negotiate separate exit settlements, say people close to the situation.

Mr Stormer, an employee rights lawyer, is known at Disney: he filed a class-action lawsuit last year for employees who worked at its theme park hotel, alleging that their work identity cards were vulnerable to identity theft and criminal abuse. He declined to comment for this story.

Ms Gates settled with Disney recently while negotiations continue with Ms Lifford and Ms Cole Hill, say people familiar with the matter. Life goes on under the new regime at DCP. Tensions between the unit and Mr Perlmutter have dissipated.

The box office and commercial successes Marvel has produced for Disney have won Mr Perlmutter admirers outside the group and strengthened his position within it. But some former Disney employees warn of collisions that may lie ahead between two very different corporate cultures.

“You would think that Disney, with all its heritage and culture, would prevail,” says a person involved in integrating the two companies. “But the common question in the hallways [at DCP] was: remind me who bought who here?”