VIDEO: '13' Reunion! Ariana Grande Surprises at Jason Robert Brown Concert

Jason Robert Brown had a surprise guest at his Hollywood, CA concert last night - international superstar Ariana Grande, who made her Broadway debut in the composer's 13 THE MUSICAL. The Tony-winning composer and lyricist was performing for one night only along with Shoshana Bean at the Catalina Bar & Grill in Hollywood, CA, presented by Chris Isaacson Presents. He is currently conducting THE BRIDGES OF MADISON COUNTY national tour at the Ahmanson Theater in LA through January 17.

Joked Brown, "I happened to bump into an international pop star the other day and I asked her if it would be fun to sing a tune or two and she said, 'three' and I said, 'three would be fine.' Below, check out Grande's performances of "The Lamest Place In the World' and "Brand New You" (featuring Shoshana Bean) from '13', and "Getting Out" from the composer's album "Wearing Someone Else's Clothes."

Brown is a Tony Award-winning composer, whose "The Bridges of Madison County," a musical adapted with Marsha Norman from the bestselling novel recently appeared on Broadway. His musical "Honeymoon In Vegas," based on Andrew Bergman's film, played on Broadway in 2015 following a production at New Jersey's Paper Mill Playhouse. A film version of his epochal Off-Broadway musical "The Last Five Years" was also released in 2015 starring Anna Kendrick and Jeremy Jordan and directed by Richard LaGravenese.

His major musicals as composer and lyricist include: "13", "The Last Five Years", "Parade," and "Songs for a New World."

Following her run in '13', Ariana Grande landed at the top with her first full-length album for Republic Records, Yours Truly. It debuted at #1 on the Billboard Top 200, Billboard Digital Albums Chart and iTunes Overall Albums Chart. Moreover, it yielded the game-changing pop smash "The Way" featuring Mac Miller. One of 2013's defining songs, the single went double-platinum, hit the Top 10 of the Billboard Hot 100 and reached #1 on the iTunes Overall Top Songs Chart. In the aftermath, she was named "Best New Artist" at THE AMERICAN MUSIC AWARDS in 2013. Her latest album 'My Everything' was released in 2015 and includes the hit single "Focus."