Lost interest in toys lately

I am enjoying Calvin being older now. He is a better playmate for Violet! They seem to have lost interest in the majority of their toys (with the exception of their train set) and love to imagine games. They pretend to be puppies, pretend to be baby/mommy, etc...and are using their minds to make up games to play together. When they are actively engaged in an imaginary role game, its great, they play SO well together! But if they're at odds and one or the other is making the other mad, its like world war three, with plenty of screaming. Violet is constantly bossing Calvin around which drives us all nuts. If they are both melting down it is usually a case of them being very hungry.