>>53590359Actually, there IS - in Crystal, anyway. You're told by the three sages that Raikou, Entei and Suicune took on forms representing the elements involved in their death after Ho-Oh reincarnated them - the lightning that struck the tower, the fire that burned through it, and the rain that put out the flames, respectively. Those motifs couldn't have already been present on them if they only adopted them after the fact, so they clearly didn't look the way they do now and clearly weren't as powerful.
Incidentally, this exact line is also proof that Walking Wake can't be an actual past incarnation of Suicune, since it still carries the rain and aurora motif that Suicune should not have had pre-rebirth.