Hippopotamus

Bouquet's shadow is Hippopotamus. Hippopotamus may be weak and somewhat cowardly, but he has the ability to shapeshift, sometimes using that ability by wrapping around Bouquet to provide her with a disguise. Hippopotamus later gains the ability to copy the attacks that he is hit by. In the second series, he and Bouquet have been given the ability to merge with Blue Dragon or Saber Tiger to provide armor and make them appear in near-full form. He also worries for Bouquet's well being whenever a battle begins.

from wikipedia