The Atellan farce, which began in the Oscan town of Atella, in Campania, was an early type of Roman dramatic entertainment that lasted into the Imperial period. Originally, Atellan farces were improvisational. They relied on simple plots, stock situations and stock characters in masks, improvisational dialogue, as well as the physical comedy of slapstick and burlesque. By the early Imperial period, Atellan farces were no longer improvisational, but scripted performances, since by the first century B.C., Atellan farce had become a literary genre.
Livy describes Atellan Farce in section 7.2. of his History of Rome. He says the Romans first performed them to try to fight a pestilence in 363 B.C.
Reference: Richard C. Beacham The Roman Theatre and Its Audience).