Improvisational comedy also called improv or impro is comedy that is performing with a little to no predetermination of subject topic and structure. The performers discover their lines and actions spontaneously, typically following a general theme and format, often in response to audience suggestions. Improvisational comedy is a form of improvisational theater.
Improvised performance is as old as performance itself. From the 16th to the 18th century, Commedia dell'arte performers improvised in the streets of Italy. Many silent filmmakers such as Charles Chaplin and Buster Keaton used this approach in the creation of their films, developing their gags while filming and altering the plot to fit. The Marx Brothers were notorious for deviating from the script they were given, their ad libs often becoming part of the normal routine and making their way into their films.