The striped dragon is called the Friendly Dragon. He was a gift to players who were invited to the game with the Invite a Friend promotion.
The krokomummies and krokotillians are pets that resemble creatures in Krokotopia, so that'd be a good place to start. :D
Again I ask, why doesn't Wizard 101 allow these pets to be bought (even at high prices if you must) after the quests have been accomplished. I understand the hipe of getting them as a "Drop" but for those of us who have been unfortunate to get such a lucky drop item, sell them once that part of the quest is over. Such as you do with the KROK pet in Kroktopia, those in Wizard City can't get those until the world of Kroktopia is opened up.