They are both based on semi-transparent flash images.
When you look at them on a solid background, in this case, the default gray, you can tell that they transparent. Here, the actual pet is on one color, while the rest is transparent, giving it a very odd and strange look.
Basically, they converted these to GIF on a grey background, when they should have done it on a white. Or, better yet, they should have kept them as PNG which would support partial transparency on any background, but I suppose too many users still use IE6.
It's hard to explain, but I'm willing to bet they'll both look much better once they are on standard white lookups.
EDIT:
Pretty sure these are the background these images are meant to be shown on, not white or light grey.
Still look fugly, but if you go
to this link and look at a faerie pet with transparent wings, you'll see a similar effect.
They still screwed up somewhere, koi and jelly pets don't usually do that, from what I can tell.