The picture on the casket disappears when the camera cuts to behind the minister.
When Dr. Kelso talks with Ted, the clock behind him reads 12:15. When he switches tables to get away from Ted and runs into Carla, the clock behind him reads 8:05. The next time the clock is seen, it shows the appropriate time.
When JD is playing cards with Leonard in his mind, Leonard lays down three of his cards next to other melds in front of him and claims "gin". In gin rummy, the winner's cards are revealed all at once when "gin" is claimed; melds are not laid down as they occur. It's more likely that they're playing regular rummy, not gin rummy.
When Ben is talking to J.D. about how his two sisters kiss, he looks at the camera for a second.
When J.D. runs away from his conversation with Turk and Elliott because he is paged with a code, he slows to a walk once he is in the doorway.
Ben's photos of himself at the Great Wall of China and the Pyramids appear to be taken in front of the same privacy glass window.