Load glitch
From Halopedia, the Halo wiki
The Load Glitch occurs in Halo 3 when a player can see an empty part of the map. This is an unloaded area of graphics. The effect is similar to being on the edge of a map where the map does not render, however this is usually in the foreground. Many load glitches can be seen when in Theater camera, and one flies to a point ahead of where the person is playing.
One of these glitches occurs on the Halo 3 level Halo. In the second building before Johnson's Warthog. In order to produce the glitch, proceed through the building but before leaving on your Warthog, go back to the door in which you arrived. Occasionally, you will see the door open but you cannot go through, and it displays screen bleed(known to game developers as the hall of mirrors effect). During a Coop game, it displays what your partner sees without a Heads Up Display (HUD). At other times when returning to the door, you will find it closed, and other times it will be open. The cause of this trigger of this is not yet known.
This also makes things all retro. When I say that i mean everything goes into a blurr.