Dragnet began as an American radio drama in 1949 and moved to television in 1951, with Jack Webb starring as Los Angeles police Sergeant Joe Friday. Its opening narration presented each episode as a true story with changed names, a device that helped define the police procedural genre on screen. The theme and narration were widely parodied in later comedy, and clips of the introduction now circulate online as shorthand for a serious investigation. Creators still use it to give an ordinary moment the weight of an official case.