Axolotl

Axolotls are like the cute anime pet you never had but always wanted, because you saw it on a deck of Pokémon cards. Tack onto that the ability to completely regenerate any dangling limb, and you've got yourself a real live Tamigachi! Another cool thing about axolotls is that they stay in their larval state even into adulthood, when they start becoming sexually mature—talk about babies having babies! Maury Povitch would have a field day with these weird sea creatures. Which of course, only makes them weirder.