Lady Gaga joked to surprised diners that she’s a “hooker . . . but one that still has to pay taxes” at the Plaza Oak Room Wednesday night. Gaga, in a barely-there bondage dress, joked about her outfit during an unannounced appearance at a show by her jazz musician friend, Brian Newman.

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Before singing “Someone To Watch Over Me,” she canoodled with boyfriend Luc Carl. A spy said, “They were all over each other, kissing. She then went to the mike holding a martini, saying she was on her fifth. But she wowed everybody with her powerful voice. Guests were going wild.”