The other night at league while playing another person this came up. I have a Skitty from Power Keepers up as my active and my opponent has Cresselia as their active. For my attack I use Tail Whip and get heads. During their turn they put Cresselia level X on top of their still active Cresselia and announce their attack. I asked another league leader/professor what should be done and they were not sure on how this should be handled. Is Cresselia level X considered a new defending Pokemon which negates my Skityy's Tail Whip or is it still considered the same defending Pokemon because it did not evolve?