When you bring it in contact with cold water it might change into a boy with really no sense of orientation.
If he runs away, your money will be gone forever.
...I love Ranma :3

Okay, so this is the old trusty method of making piggybanks with balloons and paper-maché.
Very easy, very much fun with slimy stuff and a very stylish + practical way to keep your money safe and sound.
But don´t forget to cut a hole in the base and close it with a plastic cap, so you don´t have to destroy your work when money is needed!