A kind of "hey, it's that vehicle" with one episode using the Crown Pumper fire engine that later was the first Engine 51.
Life Imitates Art: Kent McCord (Jim Reed) worked as a Los Angeles Reserve police officer later in life. Reserve police are volunteer or paid police, whose duties vary by jurisdiction. He's now retired.
The Other Darrin: Jean Reed was played by two different actresses, and her incarnation in season seven is practically Same Character, but Different. The decade can account for her radically different wardrobe and hairstyle choices, but also gone is the understanding Jean Reed who knew the risks and was happy anyway, until in the final episodes she almost seems to resent her husband's job.
Real-Life Relative: Martin Milner's son did stunt motorbike riding in one episode, and his daughter guest starred in another episode. Kent McCord's son appeared once as well. And a couple lower key ones were Tim Donnelly appearing in two episodes while his brother Dennis directed a number of episodes and Bobby Troupe guest starring while his daughter worked with the scripts.
You Look Familiar: Gary Crosby was a part-time regular as Officer Ed Wells on Adam-12 and appeared in three different roles (the first time as a firefighter, the second time as a publicity-happy paramedic, the third as an animal control officer in a Poorly Disguised Pilot) in Emergency!.