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Munch first appeared as a central character in the TV series Homicide: Life on the Street, as a homicide detective in the Baltimore Police Department's fictionalized homicide unit, which debuted January 31, 1993. The character was primarily based on Jay Landsman, a central figure in David Simon's 1991 true crime book Homicide: A Year on the Killing Streets, a documentary account of the homicide unit's operation over one year. However, Munch's storyline also touched on the book's depiction of the relationship between real-life detectives Donald Worden and David Brown, in which Worden was relentless in his tutelage/hazing of the younger detective but also genuinely wanted him to succeed and was impressed when the younger cop did excellent work. A storyline in the book involving Brown's cracking a very difficult hit-and-run homicide was included almost verbatim in the show's pilot.

Barry Levinson, co-creator and executive producer of Homicide, said Belzer was a "lousy actor" during his audition when he first read lines from the script for "Gone for Goode", the first episode in the series. Levinson asked Belzer to take some time to reread and practice the material, then come back and read it again. During his second reading, Levinson said Belzer was "still terrible", but that the actor eventually found confidence in his performance.

Munch appeared as a regular character in every season, and in almost every episode, of Homicide. After Homicide: Life on the Street concluded its seventh season in May 1999, the character transferred into the Law & Order universe as a regular character on Law & Order: Special Victims Unit (both Homicide and the original Law & Order had crossed-over numerous times before, and Munch had featured centrally in each crossover). It is explained that Munch had retired from the Baltimore Police Department, taken his pension as a Maryland state employee, and moved to New York to join a sex crimes investigation unit, where he was eventually given a promotion to sergeant.

Munch joined the BPD's homicide unit in 1983. During the fourth-season premiere of Homicide: Life on the Street, he signs up to take a promotion exam in hopes of becoming a sergeant, but a "comedy of errors" prevents him from showing up for it. In the first episode of the ninth season of Law & Order: Special Victims Unit, it is revealed that he passed the NYPD sergeant's exam, having taken it on a bar bet, and earned his promotion. He is temporarily promoted to commanding officer of the Special Victims Unit following Cragen's temporary reassignment, but is depicted as happily relinquishing control back to him, commenting upon Cragen's return, "This job sucks." He kept his rank, however, as he is still referred to as Sergeant in later episodes. He is temporarily put in charge again when Cragen is suspended after the detectives mishandle a case.

Munch makes a cameo appearance on a fifth-season episode of The Wire. Munch can be seen at Kavanaugh's Bar arguing with the bartender over his tab by referencing his experience running a bar (he opened The Waterfront Bar in Homicide). He appears in "Unusual Suspects", the third episode of the fifth season of The X-Files—the episode