Sparky is Victor Frankenstein's pet dog and the central figure of Tim Burton's 1984 live-action short Frankenweenie and the deuteragonist in its 2012 animated feature film of the same name.
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.)
