Ha! I asked the same question a couple of days 
ago! Where were you? Just joking. :)  
(If you what to check it out, it's on the 
previous page.) 

Anyway, here's the answer Largo gave me which 
makes sense: 
"Most cels have more than you actually see so that
the artist can get a better picture of what they
are drawing and so that no non-painted spots
accidently make it to the screen."

Looking at my cel -- which is coming any day -- 
the scene's an action shot of Ranma. It's 
possible that they painted more so that they 
could get more realistic movement. If you cel 
part of some action scene, it's possible that 
this might hold true in this instance. 

I wouldn't worry too much of the cel being a 
fake. Afterall, it would make more sense to 
simply paint what's on the screen, not more.