Dragon-Lion, not Lying Dragon!

As a Mutating creature resolves, it's controller
designates which is the mutated creature.
This is not determined by which card is on top
but may be tracked with a "original" counter.
Just because 702.139e makes it easier to track
does not mean I should let a power/toughness
decision control the favor of my mad-science
experiments. I can grow that lion to 6/6 size
if I want to!