These signs mark the most hazardous areas of Fribbulus Xax. Travelling through the hazard areas is not necessary to complete the game, but will let you rack up extra points and add hours of challenge and enjoyment to the game.
Found in: Keen 6
Hidden Passages Other
Some walls in the later Keen episodes actually have secret hidden passages in them.
Found in: Keen Dreams, Keen 4, Keen 5, Keen 6
Impossible Bullet Other
A bug in Keen 6 that allows Keen to fly on top of his bullets. "Jump; as you fall, look down and shoot. This may take a little practice, but once you get the hang of it, keen will 'ride' his bullet to the ground. He'll actually land just above the floor. That's good! Don't move! Look down. Then quickly look up and shoot! Suddenly keen is propelled into the air by his own bullet! Don't believe me? Try it!" - Br1ck
Found in: Keen 6
Impossible Pogo Trick Other
If you run left or right, then quickly press pogo and jump in succession, you blast off at an angle.
A game on Keen's ComputerWrist that you can play. You are a bar, and you have to block a ball and get it past your opponent.
Found in: Keen 4, Keen 5, Keen 6
Platforms are a major convenience- even a necessity on Fribbulus Xax. In most places they are used to transport you over dangerous obstacles, or to places out of reach. Many of the platforms(or "plats" as the locals call them) are still the old style which are operated by Bips. Other types of platforms occur on other planets as well.
Switches in Keen 1 and 3 only control lights and bridges; switches in Keen 4-6 only activate/deactivate platforms and bridges. Switches in K6 can be jumped or pogoed off, just as they are flicked downwards.
Keen 1 and Keen 3: The teleporters found on the maps of the games and teleport you to other locations. Keen 5: A teleportation device is hidden in the Gravitational Damping Hub of Keen 5. It leads to the bonus level on the planet of Korath III, the Secret Korath III Base. There is another return-teleporter on the map of Korath III. Keen 6: A teleporter that teleports you to an "underground" portion of Keen VI. Keen GBC: When Commander Keen uses one of these, he pops out of another one in a different area of the level in Keen GBC.
The proposed trilogy of Commander Keen that never quite got off the ground. The Trilogy was called the Universe is Toast and would have been Keen Episodes 7-9. The project was mainly shelved by ID due to more popular games like Doom and Wolfenstein 3D.