CAN BE LOCAL (2nd Controller), ONLINE, or PRIVATE
FASTEST done on Cougar Creek Railroad Prison (Train Transport Prison)
Multiplayer only areas are marked by a huge door. When you walk up to this door and press
a prompt will appear to enter a mini game. Mash alternating
to hold the door open. The second player will then run up to the gap and press
to squeeze through. Only the player entering will get the achievement. Rinse and repeat the reverse for the other play to enter the area and both get the achievement.
Fire up another controller or a co-op partner and run all the way to the far right of the train. One room before the Coal Room will be a room with the multiplayer door. Jump in an out to unlock the achievement.