South Korean pop star Psy, whose “Gangnam Style” song became a viral video sensation, celebrated this weekend by partying hard in New York with Usher and Leonardo DiCaprio. Psy also appeared on the “Saturday Night Live” season premiere. The K-pop wonder, who has signed with Justin Bieber’s manager Scooter Braun as his single went to No. 1 on iTunes, hit Circle Nightclub Friday night with Braun and Usher. After drinking several bottles of vodka with owners Bobby Kwak and Joseph Ko, Psy did several of his signature dance moves, driving the crowd wild. The rapper was dragged out at 4 a.m. by Braun, who tweeted the next morning, “#hangover.” But he and Psy were back in action after his “SNL” appearance — in which he performed “Gagnam Style” with Bobby Moynihan and Bill Hader — hitting the Meatpacking District’s 1Oak later on Saturday night, and sitting in the VIP area with DiCaprio, Stacy Keibler, Gerard Butler and Paris Hilton. Owner Richie Akiva stopped the DJs Jus Ske and Daniel Chetrit and got them to blast “Gangnam Style.” An onlooker said, “The club went wild and started doing the galloping horse dance, while Psy looked on with his hands up in the air.” Another witness said Psy didn’t dance this time but played it cool, chilling in the VIP area and swigging whiskey next to DiCaprio, who is in town shooting “The Wolf of Wall Street.”