Character mistake: The officers count the inmates and say there's 10 missing. There are indeed 10 inmates hiding in the pool. However, Pennsatucky and Chang had escaped the prison. The officers counted Linda as an inmate, who had been hiding in Litchfield the whole season, and wasn't on the list. That would make it 11 people missing, not 10.
Character mistake: When Gina tries to set up Rosa on a date, Rosa mentions the last person Gina set her up with (Justin) was a dork who rode a Yamaha motorcycle. She says "he might as well have picked me up in a station wagon." Rosa's bike is a Yamaha R1.
Character mistake: As Reddington sets up the blood transfer between himself and Ressler he inserts the intravenous line in Ressler's arm first and then in his own arm. This way the remaining air inside the line gets into the recipient's body and could very well kill him. Judging the expert way he handles the set up he should know to first insert the IV in his own arm, let the line fill with blood and then insert the IV in Ressler's arm.
Suggested correction: That amount of air would probably not cause any problem. It actually takes quite a lot of air to cause any issue.
The Committee on Human Rights - S5-E7
Character mistake: Renee refers to Indiana University as U of I. It should be IU. U of I would only refer to the University of Illinois, one of their main rivals. (00:31:00 - 00:33:00)
Character mistake: When Olivia and Dr Galina are in the bathroom, Galina mentions an umbilical chord, from a baby whose mother died (Nadia), that contained Olivia's mitochondrial DNA. Mitochondrial DNA comes from the mother, so Nadia's Mitochondrial DNA came from Letha who got hers from Marie, absolutely nothing to do with Olivia.
Character mistake: Beverly waves a university brochure in Adam's face and tells him he's going to go "to UCLA. That's in Hollywood." UCLA is in Westwood.
Character mistake: Several times Tommy addresses Sir Oswald Mosley as Mr Mosley instead of the correct Sir Oswald. Mosley never corrects him, which given his snobbishness portrayed throughout the series seems highly unlikely.
Character mistake: Lance and May walk into a bar in Massachusetts. As they enter, the camera pans and shows a large banner on the front window. The banner is advertising "game day" food and drinks. In very large letters the banner shows Boston Red Socks. The actual correct spelling is Boston Red Sox. (00:05:45)
Character mistake: Troy calls for the "Twistornado" but his card reads "Windrive"; the cards have always read exactly what the rangers called for.
Character mistake: The language peculiarity of the series refers to any wheeled vehicle as a "roller." The character "General Tak" accidentally breaks the language rules near the end of the episode and uses the word "car."
Episode #1.2 - S1-E2
Character mistake: In the incident room Danny's height is written as 4ft 8inches / 112 cm. 4'8" is 142cm. (00:06:48)
Chapter 26 - S2-E13
Character mistake: Typing letter to the President on old typewriter, Frank thinks "stared at desk" but types "started at desk." (00:24:00)