The line where Eliot says 'How was I supposed to know it was a lesbian bar' had to be inserted to explain actual injuries that Christian Kane had sustained. He was throwing a football with Timothy Hutton after a late night poker game when he slipped and fell on asphalt, grazing his cheek and splitting his lip.
Nate, playing a director as part of the con, fires off a rifle to signal "action". Director Samuel Fuller was famous for doing this.
Male members of the Leverage team comment that they've seen Irina Larenko act in a number of Emmanuelle movies. The Emmanuelle franchise is a long running series of French erotic films about the sexcapades of the protagonist Emmanuelle.
Belgrade was "played" by Budapest. When the team goes to Belgrade, the images shown of the Statue and the river with the bridge, that's actually the Statue of Liberty and the Lánchíd (Chain-bridge) overlooked by the Royal Castle, all in Budapest, Hungary.
Christian Kane (Elliot) and David Lee (Nicolas) go on to appear together on The Librarians as Jake Stone and Moriarty respectively.