Did you know that Ke$ha wrote “Till The World Ends” for Britney Spears?
Vulture interviewed her and got the scoop. "I’ve never been more proud of anything in my career,” Ke$ha explained. “When I hear my own songs on the radio I have to kind of turn it down or change the radio or whatever,” she said. “When I hear that, I fucking blow the speakers out and I order everybody to dance.”

The popular single sold over a million copies, so why did Ke$ha sell the song to Britney? Why didn’t she keep it for herself? She explained how much being a songwriter means to her, “It really solidifies me as a songwriter in the pop music world, which is what I consider myself first and foremost.”

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Click HERE to see Britney’s shocked face when she sees the set of her Femme Fatale tour!