Director Patrick McGoohan, also guest starring as an intelligence agent, inserted many references to his cult TV series, The Prisoner (1967), including saying "Be seeing you!" and, in one scene, wearing an outfit almost identical to that which had been his standard costume in the earlier program.
"Travel Town", visited by Columbo, is now part of the LA Recreation and Parks group.
Nelson Brenner (Patrick McGoohan) drives a brand new Citroën SM, US model (round, non-directional headlights), powered by a Maserati engine. After the initial craze (Car of the Year 1972 for Motor Trend magazine), it proved a commercial failure, even being banned in the U.S. in 1974. Only 12,920 Citroën SMs were produced between 1970 and 1975, when the bankrupt company was bought out by another French manufacturer Peugeot. Columbo's car is a Peugeot 403 cabriolet, and he claims there are only three others like it in the country.
When Columbo is admiring Brenner's pictures on the wall, there is a photograph of Patrick McGoohan in costume as Mary, Queen of Scots' illegitimate half-brother James Stuart, Earl of Moray from Mary, Queen of Scots (1971).
Columbo confirms his dog (who has taken up swimming in the mornings) is called Dog.