Echo the Dolphin is a character that appears in the Sonic the Hedgehog comic series and its spin-offs published by Archie Comics. She is a mobian dolphin and a lieutenant in the Meropis City Guard.
Obviously, don't nominate any human characters. Hybrids like Cheetah or The Lizard are okay, as are shapeshifters with one set animal form (eg Professor McGonagall.)
