The Broadway musical “Bright Star” had a couple of unannounced cast members for its opening night performance March 24: Steve Martin and Edie Brickell, who wrote the show, and joined the actors for curtain call. Martin slung a banjo over his shoulder, and he and Brickell led a reprise of “Sun’s Gonna Shine,” a tune from the show.

Brickell and Martin have been working together long enough – on the 2013 album “Love Has Come For You,” and on a tour with the Steep Canyon Rangers — that they come close to finishing each other’s sentences.

“We met at a dinner 27 years ago…” Brickell said after the opening night performance.

“But we started — we don’t really know, but about six years ago we started working together,” Martin finished. “It was a suggestion of Edie’s. She said ‘Let’s write a song together.’ I thought, ‘Eeeeuw, what? I didn’t know how to write a song with someone else!'”

“I don’t like to go to lunch,” Brickell put in. “I was raising my kids and moms would ask me to go to lunch. But one mom played piano, and I said, ‘I’ll write a song with you.’ And I was writing songs with her and having a terrific time, and that’s about the time I said to Steve, ‘You can really get to know someone, and be their friend, writing a song with them. I think more so than lunch!'”

They were talking at the show’s opening night afterparty at Gotham Hall, where the spread was biscuits and fried chicken and sloe gin fizzes, in keeping with the musical’s North Carolina setting. There was also a live bluegrass band, keeping the tunes coming.

The band had an unannounced guest star too: Martin again, who got up onstage with them and joined them for one more song.