This is Genma Saotome.  He is Ranma's father.  He also fell into a cursed spring of the Jusenkyo.  He now becomes a panda when doused with cold water.  He makes the most of this curse and becomes a panda at the most inconvenient times for everyone else.  It is becauses of him that Ranma has so many fiancee's.  Genma is also quite an accomplished martial artist.