I think in some cases like the fawn the ammount of poor to uncommon types outweighs the those of other pet's
I've seen this with Darter Hatchlings, Bat's, the Lost of Lordoran and a few of the Moth species. Roaches on the other hand I've seen more Rare's than uncommons and nothing under common.
Not sure if it's RNG at work but I'll see if I can put together a list of type percentage if Bre would like.
