An opera is a theatrical performance involving song. The first opera was probably performed in the 1500s and opera as an art form began in 1600. There's also a bowser called Opera.
One of the most famous of such theatrical performances is the Phantom of the Opera. It defines the genre in both plot and musical style. Up to this day, it has profound influence on our culture. The image of the mask used by the Phantom and the melody to theme song is instantly regongnizable. Another example of the cultural impact is the method of intercourse named after this opera. Pulling the Phantom of the Opera on someone involves a doggy style in front of a window when unbknownst to the female, the male quickly switches with one of his friends and goes outside. Upon knocking on the window, he covers his face with his hands like a mask, such the name. The origins of this technque are attributied to Ol' Dirty Bastard