(at around 12 mins) The picture of "young Smitty" on the dating app is a pic of the actor Brent Huff when he was in the film Das Paradies am Ende der Berge (1993)
Nolan mentions to Selina that the reason he always carry dog treats with him on the job is because of a "tip from a friend", a likely nod to his late close friend officer Jackson West who was shown doing the same in an early episode followed by saying that it was a trick his dad taught him.