Mob muscle Freddie gives Columbo a business card with "Copo Tutti De Copo" on it. It's hard to tell whether this is humor or error. The card text makes no sense in Italian; however, it is similar to "capo di tutti capi", the infamous Mafia Godfather title "boss of all bosses".
Columbo hasn't been promoted by the Los Angeles Police Department in several decades. He has been a lieutenant for at least 35 years.
One actor in this show almost matches [LINK=NM0000393] for longevity in the series: John Finnegan (who plays Sean Jarvis) had a 31-year run in the series starting in 1972. He appeared with Falk in 13 episodes and was also a regular guest actor in many popular cop shows of the '70s. He died one year after Falk.
Peter Falk wanted to play Columbo for one last time after this mystery. In 2007, he had chosen a script called "Hear No Evil", which was to be renamed "Columbo's Last Case". Unfortunately, it didn't get the 'green light' by a network, and Falk got diagnosed with dementia soon after.