The pop princess has so dominated the pop culture landscape of the last few years that it's hard to believe that all of her massive success came from just one album (which followed two barely-released efforts). 2010's "Teenage Dream" spawned something like 900 hit singles, including "California Gurls," "Firework," "E.T." and the recent hit "Wide Awake." What will she do for an encore?

- Dave Lewis