T-Rex: I had the coolest dream last night. BATMAN was in it! And ZOMBIES!
T-Rex: It was entirely great!

T-Rex: Okay, so Gotham City is infected with zombies, right?

T-Rex: People start getting bit, dying, then getting up and feasting on the flesh of the living. Batman and Robin are fighting them off as best they can, and while they're too fast and acrobatic to be touched, there's too many zombies to kill them all. They start rescuing as many people as they can, taking them to the Batcave for safekeeping. It's a good place because it's not only big, but protected and hidden!

Utahraptor: So what happens next?
T-Rex: Well, soon the Batcave is getting pretty full!

T-Rex: And at some point they've rescued this guy who's been bitten, but who's hidden it. He dies, and the next time Batman and Robin come back to the Cave, they find that everyone inside is now a zombie! Their effort has been entirely futile, and everyone they've rescued is dead.
Utahraptor: Then what?

T-Rex: Batman FLIPS OUT!!
T-Rex: And I wake up, the end!