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Mega Man Battle Network 4

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Title Screen

Mega Man Battle Network 4: Blue Moon and Red Sun

Also known as: Rockman EXE 4: Blue Moon and Red Sun (JP)
Developer: Capcom
Publisher: Capcom
Platform: Game Boy Advance
Released in JP: December 14, 2003
Released in US: June 27, 2004
Released in EU: October 18, 2004

DevTextIcon.png This game has hidden development-related text.
GraphicsIcon.png This game has unused graphics.
DebugIcon.png This game has debugging material.
RegionIcon.png This game has regional differences.

PrereleaseIcon.png This game has a prerelease article
BugsIcon.png This game has a bugs page

Mega Man Battle Network 4 marked a turning point in the Battle Network series' graphical direction, as it updated all the main sprites to be slightly smaller and more colorful.

Buggy, rushed, and saddled with a terrible localization and utterly inane storyline, it's near-universally considered to be the worst game in the series. It also somehow managed to be the only licensed game in the entire GBA library that runs into major compatibility problems on the Nintendo DS - certain areas could cause freezing that lasts upwards of 20 minutes, an issue notorious enough to be officially acknowledged by Nintendo and fixed in time for the release of the DS Lite.


Read about prerelease information and/or media for this game.
Prerelease Info
Read about notable bugs and errors in this game.
Regional Differences
The original Japanese version was quite the rushed product!

Build Date

Region Version ROM Address Text
JP Red Sun v1.0 0488A4
ROCKMANEXE4 20031022

Nov 11 2003 21:54:47
JP Red Sun v1.1 0488E0
ROCKMANEXE4 20031022

Jan 27 2004 21:00:28
JP Blue Moon 0488AC
ROCKMANEXE4 20031022

Nov 11 2003 22:00:07
US Red Sun 0489E4
ROCKMANEXE4 20031022

Apr 16 2004 14:40:18
US Blue Moon 0489EC
ROCKMANEXE4 20031022

Apr 16 2004 14:36:29
EU Red Sun 0489EC
ROCKMANEXE4 20031022

Mar 12 2004 17:18:05
EU Blue Moon 0489F4
ROCKMANEXE4 20031022

Mar 12 2004 17:22:45

Unused Battles

Normally in the game's first tournament, the player has to fight GutsMan in Red Sun and AquaMan in Blue Moon on the first play. This means FireMan and NumberMan are forced to lose and their V1 cannot be fought normally. However, if the player Navi Traded with the opposite version before entering the tournament, it is possible to fight the opposite version's Navi in their V1 form. This still means that the version that traded the Navi can't fight that Navi in V1.

In the video, their battle was hacked into a generic area to force a battle with them.

Unused Sprites

Tournament Thumbnail Icons

Mmbn4 unused tournament icons.png

The game uses two sprite archives to store the icons used in tournaments. The second archive is smaller and has these two unused icons which only read numbers. The number represents the exact number of the Navi it would have represented. These two slots could have been used by the dark Heel Navi or the pink Normal Navi.

Pink Normal Navi Color

Mmbn4 unused pink navi.png

The Normal Navi's battle sprite has one unused color. The pink color suggests that female Normal Navis were planned to be included in the game's tournaments. It would actually make more sense since the game has female operators with male Navis. There is also no tournament icon for the pink Navi, meaning it probably never made it past that stage in development.

Alternate Mystery Data Colors

Mmbn4 unused battle mystery data.png

This game introduced in-battle Mystery Data. If the player doesn't destroy it, they'll get a slightly better prize from a predetermined list at the end of the battle. Normally, only a green one is used and being green means its prizes are re-obtainable. Perhaps the inclusion of alternate colors suggests that the game would have had alternate prize levels where purple is the rarest. There has never been any orange-colored Mystery Data anywhere in the game and the blue color suggests it's a one-time prize. This feature was probably removed because they reduced the amount of battles that used a regular green Mystery Data and including other colors would mean more battles would need Mystery Data in them to balance it out.

Alternate Gutsman Color

Mmbn4 unused gutsmanSP.png

Gutsman has this unused alternate color, likely used to identify the SP version. Battle Network 4 is the only game in the series to recolor SP versions of the bosses. Gutsman already has his two alternate colors after this color, meaning this unused color could have been an earlier SP version color. Also, Gutsman is registered as the second boss, which is strange because the first boss doesn't have any unused colors.

Early ACDC Town Preview

Mmbn4 unused preview.png

Hidden in the game, there is an unused preview sprite for ACDC Town. Normally, the game uses one image per location, but this one was found at the end. It is presumed to be an early version of the final image because the icon does not accurately represent ACDC Town. The town in the icon suggests the park is behind Lan's house, unlike any used version. In the final version, the park is to the west and Lan's house is to the east. No palette could be found for the sprite, either.

Attempting to color the sprite correctly yields a more accurate preview of the sprite:

Mmbn4 unused preview fix.png

Sparkman Overworld Color

Mmbn4 unused sparkman sprite.png

Sparkman's regular color exists in the game despite not actually being used. He only has this one sprite under another palette that was only used for a "hologram" before the battle with him. Sparkman never appears on the net or anywhere the color could have been used normally.

Soul Unison Karma Colors

Mmbn4 soul karma.gif
Mmbn4 souls karma.gif

The pictures on the left show some of the souls and their karma colors. In the game, there was distinction from dark and light: MegaMan's sprite would turn light if no dark chips were used and would turn dark if dark chips were used. The light color is also used for Full Synchro. In-game, Soul Unison is disabled when the player is dark and even if the player is light, the light color isn't used. All the souls except Aqua and Proto Soul have karma colors, which is strange because their position on the sprite list doesn't make them the last souls, where the idea would have been scrapped. It is impossible to make these colors show up normally in the game and they all go unused.

Unused NPC Color

Mmbn4 unused female npc pal.png

This NPC has an unused blue palette for its overworld sprite.

Unused Red Car


The cars in this game have the same three colors that are used in the first game. However, only yellow and blue cars can be seen driving around.

Removed Souls

At the end of the Soul list in the game, right before the Dark Chaos Soul, two unused Souls can be found under the names Duo Soul and Forte Soul (Forte being Bass' Japanese name); while it is possible to "enable" them by using the codes 3203BEE4 000D (Duo Soul) and 3203BEE4 000E (Forte Soul), doing so will simply turn MegaMan into a white dot or Mettaur respectively, with his abilities unchanged.

The souls were allegedly cut due to space limitations, although a similar mechanic, BassCross MegaMan, would appear in the Japanese versions of Battle Network 5 and 6 (via e-Reader cards). Concept art of Forte Soul can be found in the book Rockman.EXE no Himitsu, while no concept art of Duo Soul seems to exist.

Unused Text

Unused Gutsman Attack

The name "GutsMG" can be found at the end of the attack list. Its placement is unusual, but it's likely that Gutsman's Machine Gun attack would have been a time freeze attack as opposed to a live attack like in the final game. It is unknown if the attack can still be executed in the game.

Debug Commands

This game also has plenty of debug scripts which can be activated in the game. There is slightly different terminology used but the effects are similar.

Got the  
Entry completed
Start Prelim1
Prelim1 completed
You talked to the Navis in ACDC Area
You talked to the Navis in Town Area
Got the ____
All Mail Get
Entered on the board
Got the Humor
Got the GunDelSl
Hide Record Display
Get all key items
MetalMan minigame
Reset lot flags
Got the Subfolder
Got the C-Slider
Got Folder 2
Chip Set
Chip Set
Got the Spin items
Got HP Memry
Got RegUP3
Got RegUP2
Got RegUP1
Got ExpMemry
Start Fire Minigame
Got the DublBlue
Got the DublRed
Got the C-Slider parts
Got 50 BattlePoints
Travel around the world
Got the PA
Delete flag set
Got the NaviCust
Got the items
Got the Sub items
Got all chips

The list mentions names that aren't exactly used in the game. "DublBlue" and "DublRed" are not items or anything in the game. It is also odd that blue comes first since internally, red is first. The last entry's effect is also unknown. Perhaps it relates to a second folder which is related to the player's version?

There are also comments on the list which have no effect, but reveal developer comments:

-Hold Free Tournament. But a scenario clear flag is up, so don't continue the game.
-DarkSoul appears. However, a scenario flag is up, so the scenario cannot be continued.

A character in the game is based on Hideo Kojima, producer of the Boktai series. His character has these three lines in the debug command list:

-One day while I was on the Net, a Vampire Navi appeared in front of my Navi. It was terrifyingly powerful, but just when I thought I'd be deleted, Django came to my rescue. I'm not kidding! I have a feeling Django is fighting Vampires even as I talk.
-Django and Otenko are probably on the Net right now battling evil and I'm going to join the fight as well.
-That's it I'm going to write a sequel to Django, the Solar Boy.

The presence of these lines suggests that the debug command file is a sort of developer clipboard. Kojima's character has dialogue in-game, but they're different from these lines. These lines suggest they would have been used in sequence after major parts of the story. Perhaps his character was going to have these lines which would have made him sound more like a game producer than simply a Django fan.

Virtual Console Differences

  • Like with other games in the series, several palettes and effects were altered to reduce the chances of epileptic seizures.
    • Magma Panels now use a more orange palette and a slower palette cycle.
    • The Blinder Battle Chip only flashes the screen three times.
  • Due to multiplayer (and, by extension, trading) being impossible to achieve, selecting the "Comm" menu now gives the player one of every secret chip (with the exception of GunDelSolEX, GrandPrixPower and Duo); however, Free Tournament and powered up Red Sun/Blue Moon Giga Chips are inaccessable.
  • Putting in Left, L and Start on the title screen replaces Bass Omega in Black Earth 2 with BassXX; hacking to unlock the Mod Card menu reveals that the cheat code simply creates a blank Mod Card, fullfilling BassXX's unlock conditions.
  • All bugs relating to Navi summon chips have been fixed.