Human 1: "Huh, that was crazy how we couldn't get a blood draw on that Red Tail. There was no blood in his veins. Is that even possible?"
Human 2: "I don't know. How can you be alive and not have blood in your veins? Unless..."
Human 1: "...unless he's undead?!"
Human 2: "Oh my god, that explains it. An undead Red-Tail!"