Agent Ressler is loosely based on Robert K. Ressler, a former FBI agent and author, who played a significant role in the psychological profiling of violent offenders in the 1970s and is often credited with coining the English term "serial killer". He was also fundamental in the setting up of the ViCAP system . (Violent Criminal Apprehension Program )
Bazzel Baz, who plays Red's chief of security Baz, is a veteran US marine and a former member of CIA's Special Operations Group. He is the founder of the Association for the Recovery of Children (ARC), which rescues abducted children. In 1991-2012, they had conducted 56 successful rescues.
Creator Jon Bokenkamp loosely based Raymond Reddington character on the real-life Boston mafia boss, James 'Whitey' Bulger. As explained at the 2013 Comic-Con panel, many news stories concerning Bulger's arrest and trial were prevalent at the time. Bokenkamp tossed around a few "what if?" scenarios and came up with the basic concept of the show, anchored by the nefarious "concierge of crime" we now know as Red. Although Spader came in very late to the concept (within approximately two weeks of the principal shooting of the pilot), he can be credited with largely contributing to the final "look" of Reddington: closely cropped hair, hat collection, Rx shades (for practicality - Spader really does need them to see), iconically tailored vest-tie-trousers-shirt ensemble, and the infamously expensive ($5,000?) all-weather navy blue coat. As for the acerbic humor & raconteur tendencies of Red? Spader claims these were already present in the pilot script, however one can't help but think that the writers expanded these qualities once they got to know Spader a bit better.
The trivia items below may give away important plot points.
The 6 digit number Red receives from Wujing 042983. April 29 1983 is the real birthday of Megan Boone, the actress who plays Elizabeth Keen. This number was used by Red to access ViCAP where he found Lucy Brooks aka Jolene Parker.
As said on the FBI's top ten most wanted fugitives at the end of season two, Raymond Reddington's official charges are: sabotage, destruction of government property, conspiracy, unlawful flight to avoid prosecution, violent crimes in aid of racketeering, rico violations, weapons violations.