When Dwight discovers that Jim put his stapler in Jello, we see Phyllis turning around after Michael says "Discipline, kinky!" However, Phyllis is not sitting behind Michael and Ryan for the rest of the shot.
In the pilot, Michael states they have the whole floor, but in subsequent episodes, Vance Refrigeration is also on the second floor.
When Roy first enters, the boom mike can be seen at the top of the screen. Response: The premise of the show is that the office is being filmed by a documentary crew. The boom mike is from the documentary crew and not a goof.