The crowd at Friday night’s outdoor showing of Grease in Rosslyn got to witness an extra bit of summer lovin’ — a choreographed, real-life marriage proposal.

Multiple attendees captured the scene on their cellphones as a group of people stood up in front of the crowd and started dancing to the musical number “You’re the One That I Want.”

At first, the stunt looked like a simple “flash mob” — a group of dancers filming a viral video. But as the song wrapped up, the movie was paused and 30-year-old Tyler Pepin, of Arlington, got down on one knee and proposed to his girlfriend, Sarah.

“Sarah, you’re my best friend and you’re the one I want to spend the rest of my life with,” Pepin said, as Sarah looked surprised. “Will you marry me?”

The crowd cheered as Sarah said yes. The film resumed shortly thereafter.

“Sorry about that guys, but it was a good cause,” the projector operator said amid another round of applause for the newly engaged couple. Grease was the final flick of the season for Rosslyn’s outdoor film fest.