Oscar's shirt has a small wet patch on the right shoulder after Michael throws a segment of orange at him. Moments later, the wet patch has disappeared.
During the session with the mediator, Angela uses her stained teeth to prove that she is undertaking a "beet juice cleanse" as stipulated in her contract with Dwight, yet her teeth are normal in other shots of her during the session.
When Dwight and Angela enter their "secret spot" in the warehouse, a scissor lift sits in front of the door; when the camera moves up to reveal Jim and Pam in their nap nook above, the lift has disappeared.
When Dwight is using the drumsticks on his groin, you can clearly tell that he is wearing a protective cup.
The roots of Meredith's hair change between takes of action in the office and interviews with the documentary crew which supposedly take place on the same day, showing that days elapsed between their filming.
When Dwight lines up Phyllis, Andy, and Toby, you can see him laugh as he finishes explaining the trajectory of the bullet.