If you've ever watched Zombieland or played L4D2's Dark Carnival, then you already know that going to a theme park when the world is overrun by zombies maaay not be the best idea. ...or it might be the best idea. Especially if said theme park is Disneyland!
Check out this rad Left 4 Dead mod called 'Journey to Splash Mountain' by Dives—it's a rather impressive and accurate recreation of Disneyland. Note that you have to download all 5 parts of the mod to play.
And if you're curious about the set-up:
The Survivors head to Disneyland after hearing it is a military evacuation zone, only to find it completely overrun by zombies. Might as well have some fun while we're here.