Public service announcement: the original High School musical cast are reuniting

A baby-faced Zac Efron appeared at the opening of 'The Revenge Of The Mummy - The Ride' Gala Benefit at Universal Studios in 2004 at the age of 17.

By the age of 18, Zac had started to really work on his soon-to-be-famous smoulder, pictured here at The WB Television Network's All Star Party.

Zac did some serious glowing up in 2005, and is pictured here later that year at High School Musical co-star Ashley Tisdale's birthday party.

We couldn't leave out the High School Musical premiere in December 2005 - Zac pictured here with his co-star and on-off girlfriend, Vanessa Anne Hudgens.

Pictured here with his Hairspray co-star Brittany Snow, Zac ditched the longer locks at the age of 19 and worked even harder on that smoulder.

Just two months later, Zac had dyed his hair much darker and gone for the David Beckham mohawk at the 2006 Billboard Music Awards.

The classic Troy Bolton locks returned in 2007 for the release of High School Musical 2, pictured here at the 2007 Teen Choice Awards.

At the age of 21, Zac was looking to move away from the Troy Bolton/Bieber 'do, and fashioned it slightly more stylishly at the premiere of High School Musical 3: Senior Year.

Zac was working the quiff in 2009, appearing on The Late Show with David Letterman.

The quiff really came into its own in 2010, as Zac attended the 2010 MTV Movie Awards.

Channelling his inner Bond, Zac looked VERY dapper in a grey suit and a shorter 'do at the 2011 Mercedes-Benz Fashion Week. Not sure about the pout, though.

Zac's look stayed much the same over the next few years - until 2014, when he rocked a Sergeant Major moustache at a Los Angeles Lakers Game with Sami Miro.

Back to his old self by 2015, a 28-year-old Zac had his old wry smile on at the premiere for We Are Your Friends.

This is a rather divisive look - but it was popular at the time! It seems he was testing the waters with the blonde streaks, as he goes full platinum in 2019... Pictured here at the premiere for Mike And Dave Need Wedding Dates.

Zac toned down the blonde but kept a slightly lighter shade at the premiere for The Greatest Showman in 2017, and brought back the 'tache - but not in such a severe way.

The 30-year-old was seriously feeling himself at the Golden Globes 2018, having toned down the moustache and added a bit of all-round facial fuzz to the mix.

Seriously, who else could look this good with platinum blond hair and dark facial hair? Sigh.

Zac whacked some toner on his bonce later on in the year, going for a more silvery platinum look at a film screening for his biographical film Extremely Wicked, Shockingly Evil and Vile at the Tribeca Film Festival in May 2019.

By December 2019, it looked as though Zac was growing out his lighter locks when he posted this group shot of himself in Papua New Guinea, confirming that he'd been struck down with an illness whilst there filming Killing Zac Efron, showing him going 'deep into the jungles of a remote, dangerous island to carve his own name in expedition history'.

In 2020, Zac's travel show Down to Earth premiered on Netflix. Landing on Netflix UK on 10th July 2020, the docu-series showed Zac visiting different places across the world, including London, Lima, Iquitos, Sardinia, Costa Rica, France, Iceland and Puerto Rico.Here, Zac opted for his natural brown hair, and even grew out a beard.

In 2022, Zac appeared at AT&T's Life, Gig-ified event, where he sported his natural brown hair and a moustache.