|This article is written from the Real Life point of view|
The Debug Menu is a menu used in the Game Boy Advance Metroid games to interact with the game mechanics, such as events and energy or missile reserves. The debug menu was used for bug testing during the games' development, and was intentionally rendered inaccessible through normal means. As such, it can only be interfaced with via cheats, which means it must be used in an emulator or with a cheat device. The debug menus in both Metroid Fusion and Metroid: Zero Mission enable item toggling, which was a feature present in Super Metroid.
Entering a GameShark cheat code allows the player to activate and deactivate most items, with the exception of Suits. This indicates that item toggling was actually a working in-game feature. Supporting this theory is the fact that each Beam and the Space Jump have their own sprites and sound effects, which cannot be heard unless stacked Beams or the Screw Attack are disabled.
The Debug Menu, as seen above, can be used to manipulate the game in various ways. It is navigated via a flashing box that can select and change what is shown. Note that the supply, S-event,and Q-Save tabs on the debug menu do not have any known effect on the game itself, but do change periodically throughout the game. The H: and G: tabs are representative of the room in which Samus is in. These have not been cataloged as of yet, but may be in the future. The Debug Menu shows that Metroid Fusion is, in fact, an event based progression game, as changing the event will adversely effect what is happening within the game. Some events will trigger different Navigation Room text to appear, and other events will lock some doors or destroy some passages. Each tab can be affected by selecting it. For upgrades, white means that the upgrade is active. For number selectors, such as M_Max, each digit can be individually changed by selecting it. While a number is selected, pressing up will cause the digit to decrease by one and pressing down will cause the number to increase by one. These numbers, however, have their limits: Energy and E_Max will not go above 2099, Supply cannot be selected, Missile and M_Max cannot go above 255, P_Bomb and PB_Max cannot go above 254, Samus will not go above 18, Event will not go above 109, and S_Event will not go above 155. Samus's in game time can be changed as well, but no time above 255 hours and 59 minutes can be set.
Though beams besides the Normal Beam (which cannot be toggled off) and Wide Beam cannot be seen by themselves, adding the Ice Beam to any combination of beams that does not contain the Wave Beam will add the Ice Beam's signature light blue coloration, give Samus the Unnamed Suit, and add the sound effects that go along with the Ice Beam being charged, but it will not freeze enemies without the Wave Beam. The fully powered beam can damage some enemies uncharged that the Wave Beam cannot, such as the weakest variety of Space Pirate. Along with this, adding certain beams in without the beam before it (except for the Ice Beam and Charge Beam) will not have an effect on the beam Samus fires, but deactivating the Charge Beam will, obviously, make Samus unable to charge her beam. This is the same case with Missiles: having any type of missile active will show the missile icon, but Samus cannot fire missiles unless Normal Missiles are turned on.
The Debug Menu also shows that bosses will always spawn when Samus enters their room, as long as she does not have the upgrade that they give her. This can lead to situations where the game is impossible to complete; if Samus enters the boss's room at the event in which they are supposed to spawn, the doors will lock, and if she has their upgrade, they will not appear and the doors will never unlock. Event based bosses such as B.O.X. and the S.A.X. will still only appear in their respective events. This also shows that the Core-Xs from bosses do not actually give Samus the upgrade: during the correct event in which they are supposed to be killed, they will progress the event, changing the Samus number value, which then gives her the upgrade. If they are killed in the wrong event, the Item-Get text box will state that Samus obtained the upgrade that was supposed to be acquired in that event, even though she does not actually acquire it. If there is no item received in that event, the text box will state that the nearest security level was unlocked, but once again, this is not actually true.
Unusual effects can be produced by altering Room States. By editing the event setting, it's possible to change the room states of rooms before entering them. If a room's state is altered while Samus is inside the room, the change will not take effect until she enters an unaffected room. This allows for bizarre outcomes, such as Sector 5 being completely destroyed, rebuilt, then destroyed again in the span of thirty seconds. Accessing a Navigation Room during an event in which Samus is not supposed to be able to access one will make Adam say various things such as "Target Eradicated" or "Empty". Certain bosses also have different reactions to Samus using late game upgrades on them. Arachnus will go down in one hit of The Screw Attack and a Fully Charged shot of the Plasma Beam, or 3 Power Bombs. All other Bosses are unaffected by the Screw Attack, but all early-game Core-Xs go down much more quickly to upgraded Missiles.
Using the Debug Menu to access other areas early can have strange effects on the game's various rooms. In the area of Sector 2 that is overrun with Kihunters, during Samus's first visit, areas with Zoros and Kihunters can be seen right next to each other. If the security levels are reactivated during the blackout sequence, it's possible to see that rooms which are typically blocked off during the blackout were not given darker lighting to fit in with the other rooms.
- The Debug Menu in Zero Mission more closely resembles the Samus Screen, unlike that of Fusion.
- Using the Debug Menu for Metroid Fusion for event manipulation can cause averse effects. For example, setting the event to the Omega Metroid fight during the final countdown will cause the game to switch to the proper time, although the Omega Metroid will not appear. This bug can be fixed by exiting the ruined Docking Bays and the following corridor and using the Debug Menu to access a different event.
- The lack of Special Charge Beam Attacks in Zero Mission may have contributed to the removal of item toggling in the game.