Britney Spears had some very special guests in the audience during her Las Vegas show this weekend. Beyonce and hubby Jay-Z made a last-minute entrance before the show began. It seems Beyonce might be one of Britney Spears’ biggest fans. Singing along to many of her songs, Bey had clearly committed the lyrics to memory.

“No one had any idea that they were coming. It was a huge surprise,” a source told E! News. A fellow attendee added, “We all thought the president or Britney herself had come out it was that crazy.”

Oh yeah, @BritneySpears slayed her recent concert – just ask @Beyonce and Jay Z: https://t.co/amf7MJF72K pic.twitter.com/tLWOzUZ1BX

— cambio (@cambio) November 22, 2015

Sitting in VIP seats, Beyonce and Jay-Z had a perfect view of Britney Spears as she sang and danced her way across the Planet Hollywood stage.

“She sang the classics like ‘Baby One More Time,’ ‘Oops! I Did It Again’ and ‘Stronger,'” the source says. “She seemed very excited to hear ‘Me Against the Music’ too. She was definitely happy to be at the show.”

In September, Britney Spears announced she had extended her residency, meaning even more fans will get to see her in concert.

Beyoncé and Jay Z Went to @britneyspears's Las Vegas Show, Danced to "Oops I Did It Again": https://t.co/2bRvRV2fGf pic.twitter.com/7Gxmn77wTR

— Marie Claire (@marieclaire) November 21, 2015

“I’m not ready to leave Vegas yet! And I just really really love this show and this city,” she said at the time. “I’m so proud of the show, and my band, my dancers and my crew have all become such a family to me. When it came down to me really having to make this decision, I just couldn’t imagine ending my residency at the end of this year.”

Beyoncé knows all the words to the Britney Spears classics, just like the rest of us: https://t.co/WGQuLy9ExR

— E! Online (@eonline) November 22, 2015

Do you suppose Britney Spears had any idea that Beyonce and Jay-Z would be attending her show this weekend?

Did she know that Beyonce is such a huge fan?