I can't remember the exact specifics. And I'm probably confusing the details with a variety of stories. But basically, it featured...
1) Ranma was cursed early on
2) Ranma went to middle school with Yuka and Sayuri (maybe Daisuke and Hiroshi were there too?)
3) ~~During elementary/middle school, Yuka and Sayuri were fighting, and tumbled out the window. Ranma saved them, but broke a leg doing so.~~ Never mind, this is from Ririkaru Ranma.
4) At some point, when the Ranma 1/2 canon starts, Akane is surprised that Ranma already knows Yuka and Sayuri.
5) There may have been a scene where Azusa took "P-Chan", and Ranma tries to rescue him? While at the ice rink with Akane AND Yuka + Sayuri?
Ranma also might have been a magical girl, but I'm not sure.
Anybody have any idea what stories these could be? Anything that fits, even if it's just one or two of the above details, would be wonderful.