Getting the Red Key (17)

In the [Behind the Counter] area, defeat Pig Cops and a Captain. Find Freezer Ammo on the right garbage bin, an Atomic Health by destroying a cardboard box on the counter, another Atomic Health on a window sill, a Small Medikit on the counter near the pop machine, a Pipebomb on the slanted area behind the counter, and two Pipebombs on a cash register near the window sill.

Across from the counter, find a grate above the condiments stand. Break it to enter a shaft containing Shotgun Shells. You must squish Slimers and jump to reach the longest part of the shaft. Follow it down and break another grate to enter the [Men's Bathroom]. Defeat the Troopers, using a Pipebomb if necessary. A Large Medikit is under the grate. Open the door to fight a Pig Cop and observe the women's bathroom door blow open. Enter the [Women's Bathroom].

In the [Women's Bathroom], you will encounter two Alien Drones and an Enforcer. Do not use explosives here, as the mirror is required to progress. Find Shrink Ray Ammo on top of a stall wall. Look in the mirror for the message 'Think Smaller', which refers to a small shaft in the corner. You can be shrunk by an Alien Drone, but it is easier to use the Shrink Ray (like the one obtained with the Blue Key) to reflect its beam off the mirror. If you destroyed the mirror or killed the Alien Drone, you are stuck. Get shrunk and pass through the small vent.

Proceed to the [Kitchen], where you will face many Troopers, Captains, and Enforcers. After clearing the enemies, collect your rewards: a Chaingun Cannon behind a deep fryer, Body Armor on a deep fryer, a Small Medikit, and an Atomic Health from a destructible carton. You can also disable a Forcefield here that leads back to the Dining Room. Continue down the hall.

Go down the hallway and turn right into the [Storage] room. Here, you will find Slimer Eggs and four Enforcers, which can be defeated with Pipebombs. The Red Key and Shotgun are located on a desk on the other side of the room. From the desk, you can access the tops of some boxes containing Night Vision Goggles and Microwave Expander Ammo.