The actresses have remained close ever since meeting on the set of the Disney film franchise, in which they portrayed Gabriella Montez and Sharpay Evans respectively, and the two friends recently staged a mini reunion for Ashley's YouTube channel series Music Sessions, during which she covers various songs.

"Welcome back to Music Sessions!" Ashley beams in the video footage. "I read all your comments and you guys wanted one very special guest and so I brought her in - my best friend, Vanessa Hudgens!"

The surprise collaboration, which debuted on Tuesday (03Jan17), was also a rather special occasion for Vanessa and Ashley.

"We were really excited to do this because this is actually our first duet together," the 31-year-old continued. "We did not have a song in High School Musical, just the two of us. We always wanted one, too! So now we're here."

In the video, the pals sit cross-legged on the floor of a red tent as they harmonise on the song, which Ashley's husband, musician Christopher French, helped to arrange for the pair.

Despite moving on from the High School Musical series, both actresses have continued to show off their vocals in public, with Ashley using her YouTube series to prove she can still hold a tune, while Vanessa put her musical skills to the test in the hit U.S. TV event Grease: Live last year (16), when she portrayed bad girl Rizzo.