the stripes of the zebra seem to be dominant over the spots of the leopard. but i've seen some danios that have a stripe pattern on the upper part of the body that becomes dots on the lower part.
i've seen the head bobbing behavior that you are talking about. i don't know what it is. they aren't gulping air, it's almost like they have a cough. my danios that do it seem to be healthy, so unless it's associated with shimmying in place or not eating, or discoloration, i wouldn't worry about it.