John Travolta and Olivia Newton-John Hold Grease Revival

It's been over 40 years since Grease debuted in theaters and on Friday night, the iconic musical's stars John Travolta and Olivia Newton-John took the stage to reprise their roles as Danny Zuko and Sandy Olsson for the first time since the film's release. The pair were front and center as part of the Grease sing-along event at the Coral Sky Amphitheater in West Palm Beach, Florida, but the stars did more than just greet fans in attendance. They thrilled fans by singing for them as well in a mini Grease revival.

In the appearance, as shared by TMZ, Newton-John sang "Hopelessly Devoted to You" while Travolta sang "Sandy" and also joined the male chorus in a rendition of "Greased Lightnin". The pair also participated in a fan Q&A at the event. They will also appear at the event in Tampa on Saturday, December 14 and Jacksonville on Sunday, December 15.

Ahead of Friday night's show, Newton-John shared a photo to her Instagram of she and Travolta in costume backstage at the event, noting that it was the first time they'd done so since the film was made four decades before.

"First time in costume since we made the movie!" Newton-John captioned the photo. "So excited!!"

Released in 1978, Grease was a huge critical and commercial success with the film becoming the highest-grossing musical film ever at that time. The official soundtrack for the film ended up as the second-best selling album of the year for 1978, second only to the soundtrack to another of Travolta's films -- 1977's Saturday Night Fever. The song "Hopelessly Devoted to You" was even nominated for an Academy Award for Best Original song, though it did not win.

In addition to the film's success, Travolta and Newton-John have enjoyed a lifelong friendship as a result of Grease, something they both spoke with about to PEOPLE last year.

"When you share that kind of meteoric success -- and nothing has been able to exceed it -- you share a bond," Travolta said. "I've been through her having a child, getting divorced, losing her sister. She's been through my getting married, having children. It's wonderful and full of shared memories."

"We did something life-changing, making that film," Newton-John said. '[At the premiere] you got the feeling from the energy that something was happening. It was a huge response. I feel grateful to be part of that and to have worked with him. We've stayed friends ever since."