Ranma 1/2 is the wildly popular martial arts comedy about a
Japanese boy who, while on a training trip with his father, falls
into the cursed springs of Jhusenkyo, China.  

Now, whenever Ranma is splashed with cold water, he turns into a
girl. Warm water turns him back into a boy, but only until the
next time.  The comedy relates Ranma's troubles as he attempts to
carry on his own life while being confronted with enemies,
finances, and more sources of cold water than you dreamed
possible.

The series appeared first as a manga ('sketchbook', similar to a
comic book) and later as an animated television show in Japan.