During the reception, there is a shot involving a complicated series of dance steps in front of the camera. After many failed attempts, a dance instructor who happened to be an extra asked to teach the actors how to perform the maneuver correctly.
The trivia item below may give away important plot points.
During a scene in which their characters slap each other (Kate Hudson) accidentally hit (Anne Hathaway) straight in the face very hard. Despite that Hudson hit her with a big diamond ring on her finger, she kept shooting the scenes in pain. Hudson later found Hathaway sitting in a chair with a ice-pack on her face.