I was reading the first volume of the Ranma graphic novel (the Viz
translation) again earlier, and it suddenly struck me that two
characters changed rather dramatically in the second chapter: Kasumi and
Nabiki.

Without considering the later continuity and just going by the first
chapter and a half, Kasumi seems to be a rather short-tempered, snotty
thing ("Younger men bore me.") instead of the incredibly sweet girl we
know and love.  Likewise, Nabiki is pretty, well, "bubbly" and
boy-crazy, and doesn't mention money even once.  Admittedly, the
translation might be slightly inaccurate, but their expressions support
these observations.

All the other characters are as you'd expect them. From what I can tell,
the sisters' change to the more familiar personalities occurs right
after Akane belts Ranma with the table.  On the following page, Kasumi
is once again (for the first time) looking all kind and pristine.

Possible fanfic idea?  Probably not.  I just thought I'd mention it in
passing. :)