If you're playing on a modded server that gives you the option to chose your character, during the final map of The Passing, if you are playing as a l4d1 survivor you will be teleported to the bridge where the character you are playing as is standing. When that happens the player replaces the model and can no longer move. This also prevents you from pushing the elevator button. I don't think anything happens with Bill though, I can't remember at any rate.

Speaking of Bill, if you are playing a server that lets you chose your character, if someone is Bill and there are no other survivors from l4d1 being played, he will occasionally call out like all the other characters do when the other survivors are to far away. Also he refuses to interact verbally with l4d2 survivors. This happens on l4d2 maps only.

Creator
You can get on a wall in The Passing you need 2 people to do it
or 3 first you need to get to where the plank is then near the left rail jump near the edge and you should go in fall mode someone can jump on the rail and get you up the 2nd person gets up there and you help them up and one guy stands on the bottom and you jump to the very edge infront of you where there is no wall and you jump there and the 3rd one on the rail need to get close enough to get you up then 3rd guy jumps to where 2nd guy is then helps him up 2nd guy jumps to you then you help him and 3rd guy gets on the wall and theres no wall I couldnt desc. as much sorry i tried best i could but yeah if you can maybe test this that would be great

(Dead Center) If you're wondering about the "flaming zombies", it's a simple trick. Fire is spawned then the zombies are spawned. However, zombies don't die once they hit the kill trigger at the reception area roof. There's also enough time for them to stay alive to give the illusion of them falling off the building.

It's not worth to head back on I-16 East because no items (excluding gas and propane tanks) spawn between where you come out onto I-16 (see the highway signs) then go back into buildings up onto the ped overpass.

Next two clips are useless areas.

The chair trick is not worth the time. The horde does spawn right around the point you enter the hallway.

Dark hallway with bathrooms are the bane of all existence. There's nothing there.

(Dark Carnival) When was that vent there?

(Hard Rain) Meh.

That roof trick I think causes fall damage for some odd reason.

Truck > Zombies

Pipes > Me

Fence landing fail.

Of course.

I know it's not worth to update this guide, but that double door room is actually a zombie spawn. When I've played some Versus/regular Dead Air, I've/zombies broke down that door. Survivors never expect it.

Forest route i know before, but it's more worth it to just go through the road.

Saw the return ladder, but not the shack/tiny makeshift shelter (near the garages).

Pipe tricks in the maps I've tried and they are great shortcuts, but they are a little weird to get up to. (Blood Harvest)

The back area of the Richardson building is where people do go in Versus games. It isn't overlooked.

(The Sacrifice) Yeah those jump tricks, I knew I forgot one. Those boats are also objects the tank can punch (they act like cars but are what I call "limited cars". Limited cars are things that act like cars (instant incapped) but can only be punched a couple of times).

Useless ladder is useless.

AND the wedding part, if you press the music on the right, the witch will come at whoever started the music

and You can cut Smokers touges

I think there is a Truck and inside it theres a Jocky face printed on the wall, the game makers were meant to remove that but they have forgotten about it, its still there, but i dont know which Map, ive been looking for it since ive bought this game!

great work ;)

I think I know how to trigger the midnight riders bus (on the passing) me and a friend where on the second level and my friend didn't have the achievement Killing Them Swiftly To This Song then they got it. That might be the way to trigger it or just by playing the song.

in "Hard Rain" final stage you can back to the saferoom after trigger event and wait ship in safety