In Ranma 1/2: "Jusenkyō kara Kita Koroshiya" ("The Killer from Jusenkyo"), Kin'nee, the Muscle-sword guy, turns into a young priest when doused with cold water - including totally changing his personality.
However, others like Ranma and Genma and Shampoo etc. don't change their personalities when transformed. Ranma doesn't, as far as I know, take on the personality of the girl he turns into - he remains the same person just with a different body.
Why, then, is it so different for Kin'nee? Not only does his personality change, he also has no recollection of what he just did.
