Nemo is the titular tritagonist of the 2003 Disney•Pixar animated film Finding Nemo and a major character in its 2016 sequel. He is the only living son of Marlin and his late mate Coral.
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.)