About 7 minutes in, Jake trips over the swinging door that leads from the elevator/stairs to the bullpen because its orientation had been changed while he was in witness protection. He'd already entered through that same door earlier with no difficulty.
When Zoey Deschanel describes her car to Andy Samberg (Peralta), her seat belt goes from buckled to unbuckled and back in between shots.
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.
In the scenes with Jake and Boyle in the car, the same conspicuous back projection footage is used at least three times: a taxi cab is seen closing in fast from the right in the rear window. Twice, it's especially obvious when the scene cuts to Boyle and the undertaking cab should be visible behind him (if it had been shot in real traffic instead of back projection) but isn't.
As CJ and Holt are of the same rank, and Holt has seniority, it makes no sense that CJ could assign Holt to the night shift.
Charle's son Nikolaj was adopted from Latvia but speaks with an American accent. By age 4 he would have a pronounced Latvian accent and it would take more than the few months he's been in America to change it.
Jess states that if New York City was so great it would be the state capital, but Los Angeles isn't the capital of California either.
When the lab tech suggests binging The A-Team (1983), Jake sarcastically says he is looking forward to watching 5 full seasons of television. The A-Team only ran for a half season in its first and fifth years.