According to "Memoirs of a Geisha," the Japanese once used the word "eel" as a euphemism for the male member. So an injury in which an eel swims inside a man's penis seems like bizarre collision of reality and double entendre. But this is no erotic tale from an alternate reality; such an incident actually occurred.
A Chinese man was undergoing a spa treatment involving an eel bath (one similar to the fish pedicures that have become popular in recent years), when a small eel swam into the urethral opening of his penis [source: Pangallo]. The fish then made its way into the man's bladder. The eel was ultimately removed during a three-hour emergency surgery.
The most unusual part of the story is that this was not the first medical case involving an eel entering a penis. At least one other instance is on record.
One more bizarre ER visit to go!