Mother Monster—or Goddess of Love, as she now likes to be called—watched the "Perfume" singer take the stage at Las Vegas' Planet Hollywood as part of her two-year Piece of Me residency. "Tonight's show is gonna be a good one, I can feel it. Who's coming?" Spears asked her Twitter followers.
Gaga, 27, said she'd be rocking "long blond hair" and "androgynous wear" for the two-hour concert.
"Come hang before the show starts," Spears, 32, told her pop peer. "Can't wait to see you."
Later that night, Gaga shared a picture with Spears via her Little Monsters website. "We had so much fun at your show!" she wrote, adding the Twitter hashtag #Applause4Britney. The singer also tweeted that "Britney's dad gave us homeade BBQ, it was one of the best things I've ever eatin' in my LIFE."
Gaga wasn't the only famous face in the audience: author Katherine Schwarzenegger also showed up.
During an online Q&A in December 2013, Spears told her fans, "I would do a duet with Lady Gaga. I think that would be a lot of fun. I think she's very different and interesting and intricate."
Gaga replied via the social networking site, saying, "@britneyspears lets do this bitch its time."
A divas' duet? That's music to our ears!