Continuity mistake: Near the beginning of the episode, Roy is eating & drinking while the phone is ringing. Eventually he picks it up, then Moss comes in and throws him a muffin. Just before Moss walks in, Roy's coffee cup is on his right on the desk. The next shot, as he catches the muffin, the cup has instantly moved to his left. Afterwards, the cup is back on his right.
Continuity mistake: During the party down in the basement, after Moss has told the embarrassing Amsterdam story, Roy comes back in the room and realises nobody's laughing. He walks up to Moss and says, "What story did you think I meant?" Roy has a beer in his left hand. The next shot, within seconds, he's shaking Moss by the shoulders with both hands. There was no time frame for him to have put the cup of beer down.