A stag party was a party held for the groom before his wedding. The female equivalent was a hen night. These took place frequently in Cardiff pubs. (AUDIO: One Rule)
On Rory Williams' stag party, the Eleventh Doctor popped out of a paper cake in place of a stripper. The party turned awkward when the Doctor revealed to Rory that his fiancée kissed him. (TV: The Vampires of Venice)