Extra (1998)

Park Bong-soo (Im Chang-jung), a struggling actor stuck with minor roles, dreams of one day landing a lead. One day, he's cast as a prosecutor and is handed a fake but realistic prosecutor ID. While out drinking with fellow actor Kim Wang-gi (Na Han-il), Bong-soo jokingly pretends to be a real prosecutor. To his surprise, people fall for it. Emboldened, he begins impersonating a prosecutor and investigator, going after “social evils” in the name of justice. With the money he earns through these fake stings, he even starts producing his own film. But how long can the act last before reality catches up?