Continuity mistake: When Randy reveals that he didn't sleep with Robin, the blood from his nose switches nostrils between shots.
Continuity mistake: There is a lot of foam in the glasses when Barney pours champagne, however after camera shot changes all the foam is gone. (00:10:15)
Continuity mistake: Randy's noise bleed moves from his left nostril to his right and then back again. (00:14:20 - 00:15:00)
Answer: After running the marathon for Marshall with no training, he's allowed to ride the subway for free. While sat on the train, the muscles in his legs start to seize up after the marathon to the point it is painful to move his legs. This is why he can't move them. It's the same reason your body aches after a good session at the gym the day before.
Ssiscool ★