Hm.

So, um, Adventure Time, right? Jake the dog and Finn the human? I've only seen a couple of episodes, which I enjoyed very much, but Elias has become a big fan. I'm walking him to school this morning, and he asks, "How are Jake and Finn brothers? I mean, Finn is a human and Jake is a dog."

I mull this over. "Yeah, I don't know. Are they brothers? I haven't seen very much of it."

"Yeah," he replies. "I watched an episode with their dad in it, and the dad was a dog."

We walk in silence for another minute or so, and then he says, "What would happen if a human woman had a baby with a dog? Would it be, like, a human baby with a dog's head?" 

"Uh, no," I answer, desperately trying to keep it together. "See, sometimes different animals can have babies together, but... not dogs and humans."

His face sinks. "Awwww, man!"