Well, what Uwibami said, basically. If you're going to design a Creatu, make sure it looks similar in all stages. It doesn't really work if the first is a tiger, then the second, a leopard.
And I wouldn't make such a huge fuss about the size, everyone. :P You can just as easily re-edit the size on Paint or whatever you used to draw them in. True, the baby's far huger than the adult - but that can be changed just like the physical appearace.