A little backround:
I have two main rat breeding projects.
-Top eared (TE) high white Russain Blues
-Dumbo BEW's.

My goal is to produce Dumbo high white Russian Blues so I bred a Dumbo BEW to a TE Russian Blue and produced TE BEW's double het for Blue and Dumbo and then bred the double het's together and just got my first litter from the pairing.

This is what crawled out:




3 of these peculiar little buggers with wavy fur and curly whiskers are in the litter. Are these BEW Rexes?
If so, how? I thought Rex was a co-dom gene and neither of the parents or grand parents are Rex. How did this pop up out of no where?