Lady Gaga had a secret movie date Tuesday by turning up undetected to a Cinema Society screening of “The Great Gatsby” and meeting her boyfriend Taylor Kinney. We’re told the “Born This Way” singer “waited in the HBO screening room’s green room” before having security “whisk her to a seat via a side door next to the stage.” But before the credits rolled on the Baz Luhrmann epic, Gaga had already slipped out to avoid cameras. Later at a Brooks Brothers and Town & Country-sponsored party for the film at the Lambs Club, Hollywood hunk Gerard Butler was seen chatting up Orlando Bloom’s wife, former Victoria’s Secret model Miranda Kerr. But Butler was then spotted asking fotogs to erase any shots of them together, several spies told Page Six. “When he approached one photographer to erase the photos, they high-fived and bro-hugged,” one source said, adding, Butler and Kerr “had been standing close in conversation for 20 minutes. She was smiling.” Also seen: Pedro Almodóvar, Zachary Quinto and Tony Danza.