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Of course, we don't have to tell the pop star that because she already knows fans are eagerly waiting for their creative minds to get together on a track. Perry is guest hosting the American Top 40 this weekend with Ryan Seacrest, and answered some caller questions—one of which included whether or not the two singers have anything in motion.
"We've actually been talking about it for years, so we can't let anyone down," she said. "We have to do the best song ever. Beyond that, I think we'll definitely get around to it and when it happens, you are going to know."