Boyle's hair and eyebrows are an auburn color due to him having to dye it (after his hair went white due to stress over Jake's trial and incarceration). While in the train station disguised as a rabbi, hie eyebrows are black again, then when he removes the disguise they are back to auburn.
When she's visiting prison, Hawkins's black Mustang is seen in the parking lot with the rear emblem painted over the same color as the car (a common tactic in film and television when a brand has not paid for product placement). When she is talking to Holt on the phone after the failed train station bust, the rear of her Mustang can be seen and the emblem is missing entirely (another tactic commonly used for non-paid vehicle usage).
Charles says that the fake beard is fused to his cheeks because he used "Broadway caliber spirit gum." While spirit gum is a strong adhesive for applying prosthetics and false facial hair, it is nowhere near permanent, as the actors need to be able to remove it after each performance.
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.
The diamonds pulled straight from the pig's stomach are perfectly clean, with no stomach acid, bile, or blood whatsoever.
In the surgical room, loose diamonds are seen being removed from a pig's stomach one at a time. Diamonds in the stomach would be a powerful irritant and could cause the pigs to vomit them up before reaching their destination. That's why humans who smuggle things in their stomachs will put them inside something smooth, like a balloon or condom, before swallowing.
Jake asks the prison guard if he remember the "don't taze me, man" viral video. The actual line in the video was "don't taze me, bro."