Perhaps Katy Perry is not really a Britney Fan. Or maybe she had a stomachache or something? Whatever it was... she seemed way happier at the Beacher's Madhouse party right after the concert.

Katy Perry hit up Britney's big Piece of Me Vegas debut on Friday along with Miley Cyrus, Selena Gomez, Adam Lambert and other famous faces in the crowd. While Miley danced and sang along having the time of her life, Katy seemed completely unimpressed. It was super awkward to watch her just stand there as Britney put on one of the biggest shows of her career.

Perhaps the "Unconditionally" singer thought Britney could have been doing a better job. But if that was the case, why did Perry attend the show? Let's face it, Britney isn't what she used to be back in her prime -- but she is still the queen of pop. Perry kind of stood there the whole time with a blank look on her face as everybody else enjoyed the show.

Katy was probably too distracted thinking about her beau, John Mayer, who wasn't with her at the concert. Or maybe she was daydreaming about how she could put on a better show? Anyway, we don't think Britney will be asking Katy on a collaboration anytime soon after she hears about this.

Katy Perry actually wrote a song on Britney's new album, Britney Jean. We're sure Britney was happy to know that Katy was in the crowd showing her some support. The "Perfume" singer, who has been experiencing disappointing album sales and her I Am Britney Jean documentary being called a flop, needs all the support she can get on her Vegas residency tour.

Good luck Brit Brit, we still love you.