Guillermo likes dogs just fine, but he doesn't want to be one. Werewolves, as he'd said to Topher, are not 'dope', and they are way inferior to--

"I'm supposed to be a vampire!" he says miserably. "The Fog fucked up! She turned me into the dumbest monster, I'd rather be dead!" And he does mean dumb. The dogbrain is so strong he's seen a werewolf leap off a building because someone threw a fucking squeaky toy over the edge.