Revealing mistake: Pretty much throughout the whole show, the iron prison doors do not have any way to lock. Guards put the key in, but there is no actual lock or latch on either side of the door. Even when these doors are pushed shut, there is not a locking sound.
Oz (1997)
1 revealing mistake in show generally - chronological order
Starring: J.K. Simmons, Ernie Hudson, Terry Kinney
Visible crew/equipment: Simon brings Kenny to Jefferson's cell to meet his new roommate. When Kenny tells Jefferson he wants to be part of his crew and says, "I want to be G," the reflection of the boom operator holding up the boom pole/mic is visible on the glass door during the conversation. (00:24:50)
Augustus Hill: OZ. The name on the street for the Oswald State Correctional Facility, Level 4.