When Charles meets Cousin Sam, Sam's shirt is tucked in, then later when Gina walks in, his shirt is untucked.
When Jake is attempting the "Full Bullpen," Rosa can be seen covering her face with her hands (likely to hide the actress's laughter). When the shot changes, her arms are suddenly down by her sides.
The bullpen floors are being waxed at the start of the cold open, which Jake takes advantage of by sliding across the floor in his socks. Actual floor wax is soft and sticky until it has time to settle. Depending on the type of wax used, it takes anywhere from 4 to 24 hours to cure, though Jake is seen sliding across it while the waxing is still being done. Also, furniture (such as all the desks and chairs) should be removed before waxing, as the wax will create a seal around it and adhere it to the floor. Finally, the floor can be seen to have scuffs and marks on it even though it is supposed to have been freshly waxed and buffed.
Captain Holt wears his Commendation breast bar above his World Trade Center Breast Bar. When the WTC bar is worn, it is worn above all other medals, but below the American Flag bar.
Terry says that all the "T"s are silent in Skyfire. However, previously he and Parlov recited lines from the book, naming someone called "Tolgan", pronouncing the letter T.
When Amy tells Holt that Kevin is right Holt tells her "you're fired", to which she reacts with horror. While Holt was obviously joking, NYPD captains do not have the power to terminate officers at will. Officers can only be fired for cause and after a review process by the NYPD and outside arbitrators.
Terry said he wrote DC Parlov for advice when he was a little kid, which is later stated to be 30 years prior to the events of the episode. Terry was in his late 40s at the time, so 30 years prior would have been when he was in his late teens, not a pre-teen as shown in flashback.
Terry not only always wears suspenders at work but is clearly wearing them when Jake asks him if he wants to go with him to question Parlov's ex-assistant, but when he shows up to help he just happens to not being wearing them when Jake trips and pulls down his pants.
There are 15 Boyle cousins present in Shaw's, but Charles only greets 6 of them at the start of his presentation: Bobby, Brendan, Bill, Bernard, Boy Corey, and Girl Corey.