Here's a few L4D Headcanons I really enjoy
-Coach is secretly this omnipotent god, Fueled by cheeseburgers and slices of hot apple pie. Every time you see him die, he's only pretending to make it fair for the zombies. The blood you see? what self-respecting man wouldn't carry around a bunch of ketchup packets on his back, beneath his shirt?
-Save Me Some Sugar was written for Bill
-Keith is at least 12 hours ahead of the L4D2 gang at all times. He already was on the choppers seen in the beginning of the first campaign and trailers, he was on the second to last evac for dark carnival, and In classic Keith fashion, he ends up crash-landing or finding himself in the same areas the survivors go through.
-Francis and Louis become total bros after the passing, and once they're on that island, they get really good at fishing
-Bill comes back to life at some point, becoming a coach-level threat for the zombies