There’s a lot that sparkles at “The Prom” on Broadway: the sequined formal-wear costumes, the gem-studded protest-sign props, the luminous school dance decorations for the show’s finale.

But all that glittered was rivaled after Saturday evening’s performance when two brides, gleaming in rose-gold sequins, exchanged marriage vows onstage.

Armelle Kay Harper, a script coordinator for “The Prom,” and Jody Kay Smith, an actress and singer not affiliated with the production, wanted a small wedding before a bigger ceremony in Ms. Smith’s hometown next month.

But, with the entire cast of “The Prom” surrounding them onstage, and roughly a thousand strangers looking on from the audience, it wasn’t exactly an intimate affair. For the couple, this musical that celebrates inclusivity — in it, a small-town Indiana lesbian couple face opposition to attending the prom together and get help from an unlikely source — was the perfect backdrop.