Ah, Twitter, the public playground for celebrity spats. Next up is Iggy Azalea and Britney Spears. The girls collaborated on the song “Pretty Girls,” only it didn’t live up to the hype in the way that they had hoped. It is popular on YouTube and one of this summer’s anthems, but isn’t gaining the kind of traction they would have liked to see. Iggy started the discussion by saying that you can no longer just release a song and expect it to succeed on its own merit. You need to add TV appearances and more promo, which they did not do. Britney fired back in a more passive-aggressive manner, saying that she couldn’t wait to get back to Vegas and is thankful that she has plenty of shows to keep her busy for the rest of the year. Iggy recently cancelled her “Great Escape” tour, so chances are this was a jab at the artist.