A Chinese patient put an eel into the butt hole to get sexual gratification. To what extent it worked, I have no idea, but the eel must have felt it was quite cozy up the anus and made its new home there. The patient needed surgical intervention to remove the fish.
I wonder what kind of sexual pleasure the patient would feel if the eel electrocuted the sexual organs from the inside.
Props to Best Gore member @sagar_jungrana72 for the video: