The unmarked car that Muldoon and Halloran drive is a 1958 Chevrolet Bel-Air. The police car seen taking Mr. and Mrs. Gutierrez to the precinct is a 1956 Chevrolet 210.
Harry Kadison played Det. Sgt. Arcaro in the pilot. In episode two, the role was recast with Harry Bellaver. Bellaver appeared in 136 out of 138 episodes.