Unlike all of the other Blacklisters who were fictional, Robert Vesco was an actual criminal. He fled the US in 1973 shortly before being indicted for financial fraud. He ended up in Cuba, where he was eventually put in prison for crimes there. His death was reported as taking place in 2007, but an associate claims Vesco faked his death and fled to Sierra Leone. If he were alive in March of 2019, Vecso would be 83 years old. Stacy Keach is six years younger than the real Vesco.
Reddington threatens to cut off Vesco's big toes. The cutting off of big toes dates back to the book of Judges 1:6, where King Adonibezek had his thumbs and big toes cut off by the Israelis after he was captured. It was said he had done the same thing to others while he was king, and the practice was later used by Athenians on captured prisoners.
While Dr Sands carries out the polygraph test, he smokes a Morley cigarette, the same fictional brand smoked by The Smoking Man in the X-Files.
The central plot element of pulling off a heist at the opera happens to be very similar to that of the Danish popular comedy Olsen-banden ser rødt (1976), in particular the explosive charges intended to be timed to the music and the ringleader of the bandits therefore reading along in the score. Incidentally, the Olsen Gang is also three men.
Aram says Samar is really tall. Mozhan Navabi is listed as being 5' 9.5", which is taller than most women, but not as tall as several other actresses. In fact he was using this as code for how pretty he thought she was.