The door slides open to a hoard of hungry zombies dying to wrap their chops around your pizza. Defend it with your life!
Next step: set the zombie targets up, as a firing range, on the other side of the door. Take turns trying to take them out using a NERF gun, balls of paper, or anything else heavy enough to frag a zombie!
It's still shut. The zombies are pretty loud so try shouting louder*.
* Shout louder at your own risk. Lock Paper Scissors and subsidiaries accept no responsibility for any outcome derived, directly or indirectly, from the act of shouting louder. Shouting louder may, or may not, produce beneficial results in line with your individual goals. However, Lock Paper Scissors supports personal expression and your right to be punched in the face by the neighbour whose child you'll probably wake up by shouting.