The One With The Red Sweater - S8-E2
Plot hole: They say that whoever the sweater belongs to left it behind, but in The One Where Rachel Finds Out that Ross videotaped them together it is clear that Ross is not wearing anything under the sweater, therefore for Ross to have left it behind he must have gone home topless.
Stretchcast - S1-E4
Plot hole: In the Alan Partridge "Rally Driving" section he has a large camera stuck to his helmet. He says that this is so you can see all his horrible facial expressions. However when he is in the car the camera is not there but we still get facial close-ups.