When horror master George A. Romero first announced that he was going to write a zombie comic for Marvel, one of the first questions was whether it might be set in the Marvel Universe. After all, the logic went, we've already had Robert Kirkman's hot-selling Marvel Zombies, the success of which was key to raising awareness of The Walking Dead in that series' early days. Would Romero do something like that? Could it involve superheroes? Would it be in continuity? Ultimately, the answer to all of those was no, as Romero and Marvel later revealed that the premise of Empire of the Dead would be vampires versus zombies with humanity caught in the middle (not entirely unlike Max Brooks's Avatar Press series The Extinction Parade).
But that didn't stop Romero from tossing in a wink and a nod to Marvel Comics that went almost unnoticed in the comic: the "evolved" zombie in the series, who seems capable of much more rational thought and has more problem-solving skills than previously thought possible of the living dead, is named after a famous Marvel character. That would be Professor Charles Francis Xavier, better known as "Professor X." As you can see above, the SWAT Team member-turned-more-than-human-zombie was a woman named Frances Xavier. "We used to call her X," another character says of his fallen friend who, as far as he knows, isn't wandering the earth as a zombie with a functional language center in her brain. "Anyone down here would be hamburger by now," he had said, "unless she had amazing survival skills." Of course, all she really would have had to do was stay out of the grip of zombie hordes long enough to start smelling like them and stop being food. Good thing she wasn't wheelchair-bound or that could have been a lot trickier.