Continuity mistake: In season 2 episode 11, Jake is shown doing at least 3 pull ups but in this episode he shows he doesn't know how to do one and Terry has to show him.
Continuity mistake: Just before the end credits, Boyle is walking to his desk and he places his jacket over his chair with his bag on top of the coat. The shot changes to Peralta speaking but then the shot goes back onto Boyle and the jacket has disappeared. (00:20:20)
Continuity mistake: When Jake is talking to Gina about Charles' Christmas gift situation, a female cop is walking out from the rest area twice in one scene. (00:01:55)
Continuity mistake: Because the show is filmed in L.A, the lack of snow in December is very noticeable. When the characters are outside there isn't any snow whatsoever, but when Jake, Gina, and Charles are inside the store, the audience can see the heavy snow and blizzard outside from a large window behind them. (00:07:55)
Revealing mistake: At the end, Gina makes her flame-thrower with cologne and lighter. However, she never lights the lighter and the flames still appear, as if they were just added in digitally.
Character mistake: Captain Holt calls the Pimento case "Operation 225641441636324" which he said he arrived by placing a numerical value to each letter in Pimento and then squaring it. But the perfect squares couldn't match up to Pimento since there's only 6 perfect squares and Pimento has 7 letters (plus the last 2 perfect squares don't fit the pattern of the previous 4). Nor is "225641441636324" a perfect square.
Continuity mistake: When Charles approaches Adrian about how much longer he's going to stay at his place, he knocks stuff off the desk leaving a pink folder. After Adrian takes the fork away from Charles' neck, there are now extra folders on top of the pink one.
Plot hole: Amy lets Scully place the witch in the break-room, but how could she have known that after captain Holt steals the crown out of the locker, he would go there? And not for example goes back through the window he came from.
Other mistake: Holt takes the crown out of the back of Jake's cabinet. However this wouldn't be possible as the crown was in the top drawer. This would have a back on it and it wouldn't be accessible by just removing the back of the cabinet.
Continuity mistake: When Terry's wife Sharon walks into the station, she's wearing a purple dress. When she announces her water has broken while in the interrogation room, she's wearing the purple dress. After returning from commercial break, she's still sitting in the exact same spot but now wearing a burgundy tracksuit and lavender top. (Perhaps she changed clothes because her water broke however, it's highly unlikely since she is sitting in the same place and doesn't look like she's left the room).
Answer: In reality, the Commissioner is a civilian administrator, appointed by the mayor of New York City. He (as of this writing, the role has always been filled by a man; the show gets that part right) is usually someone who has risen through the ranks of the NYPD, but upon becoming Commissioner, is no longer a sworn member of the force (the highest sworn rank is that of Chief). Since Commissioners are appointed, technically anyone can serve in the position, including Deputy Commissioners (who are appointed, in turn, by the Commissioner himself).
Update: On 1 January 2022, Keechant Sewell became the first ever female commissioner of the NYPD.