When I was young I figured out that if you put a cup of water in the freezer, soon you would have a cup of ice. My parents would find cups of water in the freezer all the time. It was a learning process though, because I would check the cup of water every five minutes. My mom would tell me that if I kept opening the freezer it would take longer because I was letting the cold out.
Guess what I am finding in my freezer ALL THE TIME NOW. It cracks me up! They too are checking the water every five minutes.