* 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.
* TheDanza: Abigail Hawk plays ''Abigail'' Baker.
* HeyItsThatGuy:
** [[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.
** [[Series/{{Frasier}} Dr. Lilith Sternin]] is the Inspector General!
** Lt. Gormley is a NYPD sergeant here...and also in a memorable scene in Film/TheAvengers, where CaptainAmerica helps him battle the Chitauri, and gives him a strategy to evacuate civilians out of the affected area.
** David Ramsey, aka Diggle on {{Arrow}}. He began his role on ''Arrow'' during his second season on ''Blue Bloods''. He has appeared somewhat less frequently since ''Arrow'' began, due to his being a character on both shows, but still remains a very important character on ''Blue Bloods''.
* TheOtherDarrin: Nicky was played by a different actress in the original pilot.
* PlayingGertrude: Tom Selleck is only 5 years younger than Len Cariou, who plays his father.
* RealLifeRelative: Jack and Sean Reagan, Danny's two boys are played by real-life brothers Tony and Andrew Terraciano.
* TheWikiRule: [[http://bluebloodstv.wikia.com/wiki/Blue_Bloods_Wiki Blue Bloods Wiki.]]
* 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.
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