There once was a man from Nantucket

"There once was a man from Nantucket" is the opening line for many limericks, in which the name of the island of Nantucket creates often ribald rhymes and puns. The protagonist in the obscene versions is typically portrayed as well-endowed and hypersexualized. The opening line is so well known that it has been used as a stand-alone joke, implying upcoming obscenities.