I don't know, I think they would use the 
production BG more then once. It's not like the 
BG is impossible to move, right? Wouldn't they 
just take the BG, put it in one scene, Then, if 
they need it for another scene, just move it? 
When they sell the Cels, obviously only one cel 
can have the Production BG. But, when there 
filming it, they could put that BG behind more 
then one cels, I may be wrong, but I'm pretty 
sure that's how it's done. Any one else have 
opinions?