The prolific John MunchDEC 09 2008

According to IMDB and Wikipedia (here too), Richard Belzer has appeared as Detective John Munch on ten different television shows, more than any other character on television. An exhaustive John Munch viewing would include shows from the following programs:

Homicide: Life on the Street
Law & Order
X-Files
Law & Order: Special Victims Unit
The Beat
Law & Order: Trial By Jury
Arrested Development
Paris enquêtes criminelles (aka Law & Order: Paris)**
The Wire
Sesame Street

Belzer surpassed John Ratzenberger and George Wendt, who played barflies Cliff Clavin and Norm Peterson in six different series: Cheers, St. Elsewhere, The Tortellie, Wings, The Simpsons, and Frasier. (Ratzenberger apparently enjoys continuity; he's done a voice in every single Pixar movie, nine in all.) Munch/Belzer have been prolific in the matrimonial arena as well. Between the two, they've been married seven times (Munch:4 and Belzer: 3).

** It's unclear from the sources that I read if Munch has appeared on this show or will appear in the future.

Update: Two more things. The Munch character was inspired by real-life Baltimore homicide detective Jay Landsman...who both inspired another character on The Wire (named Jay Landsman) and appears in The Wire as a police lieutenant. All three -- Munch, the fake Landsman, and the real Landsman -- appeared in a fifth season episode called Took. Oh, and Munch, like many other television characters, is a figment of an autistic kid's fertile imagination. (thx, scott & logan)