Was two years ago. I had this room mate mark back in Ontario, I went to the hardwear store and bought one of those toilet packs you put in the reserve tank that turns the water blue when you flush. I broke a small chunk off it. Unscrewed the shower head from the arm, pushed the small chunk up the shower arm and screwed the shower head back on. He took a shower and about ten seconds in the water came out blue and dyed his head shoulders and most of his body blue in a few seconds before he realized what happened. He was laughing more then he was mad but he was kinda blue for a few days.