A hen night, or hen do, was a party held for the bride before her wedding. The male equivalent was a stag party. On Gwen Cooper's hen night, she was bitten by a Nostrovite. The party her friends arranged for her included drinking and a male stripper. (TV: Something Borrowed)
At several hen nights she attended, Clara Oswald sang "Hungry Like the Wolf" karaoke. Professor Grisenko, who was from 1983 Soviet Union, had no idea what "hen night" was. (TV: Cold War)
River Song was chased across the galaxy by a group of Sontarans after she asked them if they were on a hen night. (TV: Last Night)
Helena celebrated her hen night for five days with Andy Hansen, Erimem, and Olivia on The Station in the 34th century. (PROSE: The Three Faces of Helena)