The singer took the bride-to-be and a group of pals to immersive theatre show Queen of the Night at the Paramount Hotel and enjoyed a racy night out.

A source tells New York Post gossip column Page Six, "Katy and her group took tequila shots and selfies all night. Katy made sure the bachelorette was... spanked by one of the performers. And as the instigator, Katy set an example, getting spanked, not once, but twice."