Usually when celestial bodies crash into each other, the results are catastrophic. But Cher sang one of ABBA's greatest hits it was pure delight.

The Dark Lady appeared at CinemaCon in Las Vegas this week to promote Mamma Mia: Here We Go Again, and floored the crowd with a live performance of "Fernando," which she also sings in the movie. (The sequel to the hit 2008 film opens nationwide on July 20.)

Channeling her own 70s realness, Cher appeared magically from behind palm fronds at Caesar's, decked out in a glitter pantsuit and platform heels and flagged by a troop of dancers. The performance started with uproarious applause and ended with balloons descending from the rafters. Because Cher doesn't do half-measures.

Joining Cher in the film are Amanda Seyfried, Pierce Brosnan, Christine Baranski, Lily James, Julie Walters, Colin Firth and, of course, her Silkwood co-star Meryl Streep.

Below, Baranski reveals what it was like hanging out with Cher on set.