My then boyfriend was taking the Loop home from work one night, when he felt a suddend pin prick on the back of his neck. He raised his hand to slap the spot and felt his legs buckle underhim.
It was so crowded, that he did fall down, unconscious until the next stop when people left the train. He caught site of a short, small statured man in body paint stepping off the train with the crowd...
Luckily he was taken to the ER in time...
cheers!