You can fall into darkness on Gricklock just like on Clock Tower. This can be done at all three trucks, but is best if you try not to do it at the one closer to the spawn where you must turn right, as it is "lower" than the others. While you are in darkness, it is possible to reappear on the map by looking down and walking in any direction. Note: This is not guaranteed to happen. If you reappear, it will be at the ledge of the map, near the plant boxes.