Other mistake: Even when you beat both Shiva and Deadshot they're shown on TV monitors at Joker's meeting in the penthouse suite of the Royal Hotel.
Continuity mistake: When going to the Gotham City Bank, the clock tower bell will begin to ring. Alfred then contacts Batman and says that it's now 12:00 AM and wishes him a merry Christmas. If you look at the clock tower, however, the clock says that it's only 9 o'clock.
Blackgate Prisoner: Jingle Bells...he he he... Batman smells...he he he.
Batman: No.
Question: How does Copperhead know Joker took over Black Mask's mob?