Usually, when you pause a NoaDev game, all objects/enemies on the screen stop in their place, and continue normally after you unpause. However, @Merl_ has found out that:

• If you start a level while the game is paused - all enemies that are attached to the ceiling will fall down, and will start walking on the floor instead. This also affects the end-goal blob in the same way. This can be achieved easily by pausing, restarting the level, and then unpausing once the level is fully loaded.
• Pausing will pause cannons from shooting missiles, BUT any missile that is already in the air will continue moving, even when the game is paused. While the game is paused you cannot die, so missiles can go through you safely while the game is paused.
• Every "fire block" has a repeating cycle of a few seconds, where the fire turns on and off. If you pause the game and wait for a few seconds, this will trigger the next fire cycle immediately. So you can pause the game in specific timings, so that fires will be deactivated when you want them to be.

Because those pause-glitches can break lot of the levels, all full-runs and ILs are now separated with "Pauses" an "No pauses" categories.