10 Bombshells From New Disney Book: From 'High School Musical' Drama to Demi Lovato's Mental Health Struggles and More

Ashley Spencer's new book Disney High: The Untold Story of the Rise and Fall of Disney Channel's Tween Empire delves into the lives and careers of former child stars as they made their way to the spotlight in the 2000s through the cable channel. The new material also highlights the vicissitudes of fortune before the young celebrities turned into household names.

One shocking part was about Zac Efron and his journey to score the lead role in the hit film series High School Musical.

"He didn't have any of that Hollywood polish at all," casting director Natalie Hart said of Efron. "It's sort of what endeared him to us, because he was just a good guy and a lovely kid."

Efron, who was only 17 at the time, did not make an instant, positive impression due to a gap between his teeth and his shaggy hair. He was also not a singer. Determined to get the role, he underwent a makeover and even worked on improving his vocals — although his voice ended up getting swapped out of the final film.

Shocked and hurt, Efron "was the only one deemed unsuitable to fulfill his singing duties . . . [Disney had put him] in an incredibly awkward position," said Spencer.

According to the new Disney book, the executives wanted to have a High School Musical leading man with a more "athletic build," and they set eyes on Jesse McCartney.

Prior to the auditions for the series, McCartney reportedly received an offer to play Troy Bolton's role. However, the "Beautiful Soul" hitmaker turned down the offer because he did not want to be known as a "Disney Star."

McCartney also got a proposal to lead Camp Rock, but he declined again.

Spencer divulged more shocking details about High School Musical, including the sweltering conditions the stars and performers endured when they filmed on a location at a Salt Lake City high school one summer. There was no air conditioning at the time, and there were only portable AC units in the hallway where everyone cooled off during breaks.

"We were pushed to our max," said Corbin Bleu.

Following the film's success, the film's young stars held a media tour and planned to have a 50-plus-date concert trek.

Lucas Grabeel disclosed, "They worked us so hard, I mean, we didn't really have days off."

"Even for those who make it look easy while in the throes of the 360-degree circus that came with being a Disney Channel star, it was a years-long exhausting grind, the effects of which followed many into adulthood," Spencer wrote.

Aside from High School Musical stars, Hannah Montana lead Miley Cyrus also went through the same grueling setup.

"She filmed the show during the week, and on weekends and hiatuses did mini concert tours and appearances, filmed movies, attended media events, posed for photo shoots and recorded new music," said Spencer.

Executive producer Steven Peterman told the author that nobody ever knew how much was on Cyrus' shoulders and "how much she had to carry for a long time."

Peterman added, "There were times when Miley was being pulled in three directions. One was the necessities of filming the show. One was the Disney appearances and recordings. And once she blew up and had her separate management, they had their own agenda . . . And her family was a little nervous about saying no to people because nobody knew how long this was going to last."

Demi Lovato, who rose to fame through the short-form series As the Bell Rings, expanded her career as soon as the network executives heard her sing.

In 2007, they tapped her to lead the musical movie Camp Rock and her sitcom Sonny with a Chance. However, As the Bell Rings showrunner Danny Kaplan grew concerned about Lovato's mental health after noticing her eating habits and moods on set, prompting him to warn the network about the side effects of the bigger launching pad for the then-young star.

"Honestly, there were signs," Kaplan told the author. "But, I don't think anybody really did much about it."

Spencer, on the other hand, noted how Lovato suffered from different issues during her time on the Disney Channel, including self-harm, bulimia and substance abuse.

Raven's Home and That's So Raven star Raven-Symoné underwent two b----- reductions and liposuction before she turned 18 in 2003. While Disney reportedly did not say anything about her body, she clarified it was the public, media and her father commented about her weight.

In 2011, Selena Gomez was hospitalized due to exhaustion.

Shia LaBeouf also endured hardships, having to audition repeatedly to keep his role and being forced to do callbacks even after he had already begun filming the show.

"It's an exploitative business," Even Stevens showrunner Marc Warren said in the book. "There's that one-thousandth of a percent of incredibly talented kids who are driven and are born to do it. A kid like Shia, he was doing standup at 10. He was born to it, and it screwed him up. But would he have been screwed up if he wasn't an actor? Maybe worse. Probably worse."

At one point, a casting director found him crying between two filing cabinets, asking what he had to do to prove himself.

On the brighter side, the book also disclosed Lovato's love for Kelly Clarkson that she created an email address based on the American Idol alum's name. After Clarkson won the show in 2002, the "Heart Attack" singer made the account "littlekelly."

Former Columbia Records president Steve Greenberg told Spencer he worked with kids whose parents "are very involved," and those included The Jonas Brothers.

The author said Kevin Jonas Sr. guided the siblings to align their public image with their family's values. But after the creation of the concert film Jonas Brothers: The 3D Experience in 2009, the patriarch became worried his sons would be painted "as too sexual."

"A lot of times you could see their nipples because they’d be wearing fitted shirts, and they would be soaking wet,” tour photographer Elise Abdalla said in the book. "Their team would be like, 'No, you have to crop it. No nipples.' Anything that was too s--- was out."

Brenda Song was tapped to costar with Andrew Garfield in The Social Network — something that did not sit well with Disney Channel. The Suite Life of Zack & Cody creative consultant said Song did the film despite the network's refusal, explaining the Secret Obsession star only wanted the company's blessing and not its permission.

Spencer wrote how close Hilary Duff and Lalaine were when they worked together on Lizzie McGuire, adding, "they lived near each other and shared milestones like shaving their legs together for the first time."

However, things changed when Lalaine showed off her singing skills by singing "Reflection" in an episode, leaving the A Cinderella Story actress and her mom upset. In addition, Lalaine's relationships with their costars made Duff insecure about her, igniting emotional politics until they ultimately fell out.

Lalaine was also let go from her contract six episodes earlier than what she initially signed.