The cast of HBO’s “Game of Thrones” congregated in town last week to celebrate Season 3, which debuts tonight. After racy scenes won the series many fans and an “SNL” spoof, John Bradley, who plays pudgy Samwell Tarly, said of further nudity this season, “I hope so. If not, I’m going to be sorely disappointed.” Natalie Dormer, who plays buxom Margaery Tyrell — who could be betrothed to horrid King Joffrey Baratheon — was more resigned, saying of the nude scenes, “The work is the work, that’s the way it is.” Kit Harington, who plays Jon Snow, also made the event, which saw the opening of an exhibition of pieces from the show at 3 W. 57th St.