All Good Things... (1) - S6-E23
Revealing mistake: During the scene when Jen is telling Jack about her illness in the hospital room, she asks him to get into bed with her and talk. As he does that, Jen lifts her right arm to allow room for him. There is a tube attached to her right arm at the inside of her elbow, that is supposed to be going into an artery. But you can see that the end of the tube is actually pointing the opposite way, and sticking up through the tape pointing towards us. Obviously this was because they couldn't actually insert the tube into Michelle's arm for the scene.
Answer: Pacey.
Nick N.