Ke$ha penned the wildly popular dance-ready track, which has spent 14 weeks on the Billboard Hot 100 chart, the majority of the time and currently in the top 10. The brains behind the club-banger revealed to Vulture why she didn't keep the undeniably radio-ready song to herself for her own album. "That song," Ke$ha explained, "I've never been more proud of anything in my career. It really solidifies me as a songwriter in the pop music world, which is what I consider myself first and foremost."
OK, so she thinks of herself as a writer first and a singer second, go on ... "So it actually is really, really exciting for me when I hear [Britney] sing it. Like, when I hear my own songs on the radio I have to kind of turn it down or change the radio or whatever. When I hear that, I f---ing blow the speakers out and I order everybody to dance," K Dolla admits.
Watch Britney Spears' 'Till the World Ends' video.