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Well, the physical similarities aren't as obvious now - the star touched down at Sundance Film Festival having bleached his hair and he looks pretty different.
Efron arrived for the debut of his upcoming movie, Extremely Wicked, Shockingly Evil and Vile - a film based on the life and horrific deeds of the notorious Bundy.
The 31-year-old former Disney star has really grabbed attention at the Utah-based film festival - a quick look at social media tells us people simply can't get over him sporting a platinum blonde barnet.
"Zac Efron blonde I'm speechless," one person tweeted.
Another said: "Zac Efron's blonde hair shouldn't work....but it's got this old married lady swooning this morning."
While a third posted: "I've never pictured #ZacEfron as a platinum blonde but I AM INTO IT."
The Greatest Showman actor appeared with his co-star Lily Collins for an interview with The Hollywood Reporter. When he was asked if he'd taken on the new look for an upcoming role, he simply replied: "It's just for life, bro."
Extremely Wicked, Shockingly Evil and Vile follows the story of Bundy who murdered and raped at least 30 women and girls during the 1970s, later going on to defend himself in court.
Thirty years ago, Bundy was executed via the electric chair for his crimes, after making two dramatic escapes from police custody and having confessed to 30 homicides following more than a decade of denying the murders.
The film is told through the eyes of Elizabeth Kloepfer, played by Collins, who was Ted Bundy's girlfriend and suspected him to be the unidentified murderer authorities were looking for, prior to his capture - she even once called the police on him.
A trailer for the movie was recently released, but a scene where Efron takes his shirt off - revealing his... umm, well-sculpted body - left viewers concerned about the casting for the film.
The idea of Bundy being presented as 'ripped' and attractive seems to have left people worried that the film is 'glorifying' the serial killer.
However, although it may be difficult to believe given his horrific deeds, at the height of his infamy Bundy was often considered to be charming, charismatic and even good-looking.
It was his charm and looks that often helped him coerce many of his victims into going along with his requests - ultimately leading to their deaths.
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