Continuity mistake: At the bar, when Robin is telling the gang about Mike, Marshall's beer moves from in his hand to on the table between shots. Also, the amount of beer in the glass changes frequently depending on the camera angle.
Nothing Good Happens After 2 A.M. - S1-E18
Continuity mistake: When Ted arrives at Robin's apartment the amount of greenery sticking out from his shopping bag keeps changing between shots. (00:10:00)
Okay Awesome - S1-E5
Continuity mistake: When they first arrive at the club we see Barney, in close up, undo some of his top shirt buttons. A few seconds later, he is seen in the background with his shirt buttoned. (00:05:30)
Continuity mistake: When Lily is making the layered salad, in some shots the layers are defined, but in others there is much more mayonnaise running between the layers. (00:07:30)
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 ★