The polka-dot-wearing actress makes a cheerful arrival to the Late Show with David Letterman. Plus: Blake Lively, Gavin & Gwen, Nick Jonas and more

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Michael Cera could easily blend in with the crowd waiting outside the Late Show with David Letterman, where the understated actor chatted up his new comedy, Nick and Norah's Infinite Playlist, on Monday. The movie hits theaters Oct. 3.