Last week, Rihanna and a group of friends hit up a New York City joint called Caviar Russe, where they enjoyed champagne, sashimi bites . . . and, of course, caviar. She asked the staff to stay past closing, and they eventually wrapped things up at around 2:00 a.m. Since they were cool about staying open for her, Rihanna paid them back by helping them close. A so-called “source” says she was cleaning up and pushing barstools back into place for them.