* ActorAllusion: Frank's mention of being a Marine with service in Vietnam. During ''Series/MagnumPI's'' run, Tom Selleck often wore a cap with the legend "VMO-2", which was a Marine Forward Air Control squadron out of Da Nang.
** [[Series/BandOfBrothers Carwood Lipton]] is now an NYPD detective.
** [[Series/ThePretender Jarod]] is a detective, too ([[GeniusBonus or is he pretending?]])
** Special Agent [[Series/CriminalMinds Elle Greenaway]] guest-stars as a Russian mob queen.
** [[Series/WhiteCollar Alex Hunter]] appears as a nightclub owner.
** Frank shares a brunch with Matt Walton, better known as the Optimum cable commercial guy.
** ADA Erin Reagan-Boyle is the HotScientist in ''Film/IRobot''.
** [[Series/NYPDBlue Det. Sgt. Martinez]] must have gotten a demotion to Patrolman.
** [[Series/TheSopranos Artie Bucco]] got a new job as an NYPD Bureau Chief.
* RealLifeRelative: Jack and Sean Reagan, Danny's two boys are played by real-life brothers Tony and Andrew Terraciano.
* YouMightRememberMeFrom: Creator/TomSelleck's role as Police Commissioner Frank Reagan is his first major role in quite a while, apart from a string of TV movies based on the ''Literature/JesseStone'' book series. He mentioned in an interview on ''Series/TheTalk'' that he took the job partly because the script made him cry.