For some reason the description on this pic got swapped out for the one used by the Charybdis-Mesume pic which followed it.  Since I can't remember what was said after all this time, I'll sum up.  Ranma as a sexy Devil-girl of some sort, the hows or why's unexplored and unexplained.

E: I keep forgetting to mention it, but Ranma was created by Rumiko Takahashi.  I'm not going to bother with a pointless pseudolegal disclaimer though.