She had already worked with Hairspray director Adam Shankman on the Disney film The Pacifier.
With her role in Hairspray, her musical side is shown in several numbers including a solo entitled "The New Girl In Town", a song previously cut from the Broadway musical version.
Zac wrapped his arm around his former Hairspray costar as they walked to the event.
While the two looked cozy, the outing was most likely purely platonic as, last we heard, Brittany was still dating Teen Wolf star Tyler Hoechlin.
costars were spotted getting cozy during the evening outing. Hollywood's famous platonic pairs Efron, 25, wrapped his arms around Snow, 27, and gave her a big hug from behind.
The actor dressed casually in a gray hoodie and jeans, and was snacking on a caramel apple treat.
Plus, Brittany and Zac have been close friends for many years, ever since they starred in 2007's Hairspray together.
Back in September, reports emerged that Zac had completed a stint in rehab for an addiction problem earlier this year.
It was recently announced that Zac went through a rehab program for several weeks to try and clean himself up after allegedly doing cocaine for more than two years.
He kept his struggles a secret for awhile, including when he promoted his latest flick, Parkland, at the Toronto International Film Festival last month.
While Zac hasn't openly talked about his addiction issues, he did hint that the rehab reports were at least partially true when he thanked fans for their support on Instagram.
In 2012, Snow starred in the musical comedy film Pitch Perfect, as a cappella singer Chloe, alongside Anna Kendrick, Anna Camp, Rebel Wilson, Alexis Knapp and Skylar Astin.
She reprised her role in Pitch Perfect 2 (2015) Snow has spoken openly about her battles with eating disorders and co-created the Love is Louder Movement with The Jed Foundation to support anyone feeling mistreated, hopeless, or alone.