From The TimeSplitters Wiki

There are many glitches, though the most include the use of the only vehicle in Arcade: Its Buggy.

- Blue Base: To get "inside the inside" of the base, you must drive the buggy into the small crevice between the long wall and Blue Base. The vehicle should be stuck in the crevice, continuously attempting to drive by itself into the side of the base. Get out of it and be sure you can step into the wall, and Viola`. Now you are inside the inside of the base, though in a different dimension. Other players can only see your tag above your character. You are virtually invisible!

Cool Tricks Check it out, and you'll see a weapon to the far side of the glitched area. Run to the edge of the glitch and be sure you are aligned with the weapon. Now, run to it! Instead of falling into the abyss of the level, you can make it to the platform and grab the weapon. Now turn left from there, and you'll see the entrance of the base to the far left. Run straight forward until you are adjacent to the entrance. You should not have died, making it across the invisible bridge. Now, turn left and go into the entrance. You have gone back into the "real" dimension of the level. Just look behind you. Now you can see the entrance, along with the inside of the base.

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- Yellow Base: One can virtually use the same method used at Blue Base here, at Yellow Base. The only difference is that one must get the buggy to climb the rock wall to the left of the base, and step out of the vehicle while it is situated parallel to the base wall. One can basically do the same tricks used in Blue Base, though there is a feature of it that is unique:

The ability to shoot from the other dimension into the "real" , allowing one to kill unaware players. n00bs are easy targets using this method, though it can be risky. Since the wall of the level is still between the other dimension and the "real", one must take special precaution into coming in contact with it. Since one can shoot from between the dimensions using the wall, and if he/she were to be hit by a stray bullet (or otherwise direct shot from a veteran to the level), the impact would not only inflict heavier than normal damage, but increase the risk of the player flinching enough to pass through, completely, into the real dimension, thus breaking cover and exposing oneself.

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- Siberia Dam

Grey land This doesn't help you win the game, but it actually helps you lose, but it is fun. You end up commiting suicide in a gray area and seem to fall to your death. This is a pretty tricky glitch, first, get the buggy on the dam, then, with alot of skill, try to get the buggy to have its back wheels on top of the wall on the back of the dam (the one that has sky behind it). Then get into to buggy, if it works, you can get out and fall down this gray area and die.