While Detective John Munch is talking about Baltimore with Captain Donald Cragen and Detective Brian Cassidy, the camera shows Cragen. There is a shadow (of Stabler) on the door behind him as if he had just walked in. A few seconds later, Stabler walks in the room again, this time much farther back behind Cragen.
Detective John Munch was a Baltimore Police Detective who transferred to NYPD as a Detective. NYPD don't accept lateral transfers. A person has to apply, and if accepted, go through the academy and start out as a rookie police officer.
Detective's Benson and Stabler are at Rikers interviewing an inmate. Benson is taking notes and you see her "writing", pen pressed to the pad, then she lifts the pen off the pad and clicks the pen. When she does this the pen comes out. So the entire time she was "writing" nothing could have been written.