Zac Efron was spurred to date ‘High School Musical' co-star Vanessa Hudgens despite having a girlfriend

NEW YORK CITY, NEW YORK: Zac Efron and Vanessa Hudgens' teenage romance was a rollercoaster of emotions, both on and off-screen, as revealed in Ashley Spencer’s new book 'Disney High: The Untold Story of the Rise and Fall of Disney Channel’s Tween Empire'.

Nearly two decades after their on-set chemistry sparked real-life feelings, new details about the early stages of their relationship have come to light.

Zac Efron confided in 'High School Musical' choreographer about his feelings for Vanessa Hudgens

According to Ashley Spencer, Zac Efron and Vanessa Hudgens began developing feelings for each other while filming the 'High School Musical' franchise in 2005.

The young actors, cast as the iconic duo Troy Bolton and Gabriella Montez, found their off-screen lives mirroring their on-screen romance.

The revelation came when Efron confided in 'High School Musical' choreographer Charles 'Chucky' Klapow after a particularly eventful cast party.

Following what Spencer described as "a rare, wild night of intermingling," Efron, now 36, sought advice from Klapow, now 44, about feeling torn between his blossoming feelings for Hudgens, now 35, and a girl he had been dating back home.

"I don’t know what to do, man. Vanessa is super into me, and I have feelings for her, too. I don’t want to do the wrong thing with my girlfriend," Efron allegedly told Klapow, as per OK Magazine.

Caught between maintaining professional chemistry with his co-star and managing his personal relationships, Efron was in a tricky situation.

"I also don’t want to shut Vanessa down and ruin the chemistry in the movie," he added, as reported by Spencer.

Charles Klapow encouraged Zac Efron to 'explore' his connection with Vanessa Hudgens

The 'High School Musical's choreographer, recognizing the complexities of young love, encouraged Zac Efron to follow his connection with Vanessa Hudgens, reasoning that they were all still young and far removed from their usual lives while filming in Utah.

He advised Efron to "explore" his relationship with Hudgens despite the circumstances back home.

The night escalated into an emotional whirlwind as the cast continued to hang out at their hotel.

According to Spencer, Hudgens broke down in tears, locking herself in the bathroom with her close friend and co-star Ashley Tisdale.

"Vanessa was in tears, crying in the locked bathroom with Ashley," Spencer described. "It seemed as if the tipping point of her unrequited love had been reached."

As the night unfolded, another cast member Corbin Bleu, attempted to comfort Hudgens, while Efron eventually stepped in, knocking on the bathroom door.

After Tisdale left the two of them to talk, Efron and Hudgens emerged hand in hand. Fellow cast member Lucas Grabeel, who played Ryan Evans in the films, remembered the moment clearly, capturing the high school-like intensity of the situation.

"I mean, it was so high school," Grabeel recalled in the book. "It was like, 'He broke up with his girlfriend, and we’re together now'."