MB, nicknamed Melissa Bergman, is the main antagonist of Metroid: Other M.
The Bottle Ship incident
Samus Aran first saw MB watching her from a window overlooking the Experiment Floor in the Cryosphere, and she ran away after realizing she had been seen. Samus gave pursuit, and tried to convince the woman that she was here to rescue her, much to MB's denial. They were separated after Samus was attacked by a soldier using the RB176 Ferrocrusher.
Later, Samus enters the Bioweapon Research Center in the Biosphere, and the woman is startled by Samus' presence. She runs behind a door and closes it. Samus once again tries to convince her that she means no harm. The woman opens the door, and introduces herself as Madeline Bergman. Samus takes her to sit down, and "Madeline" informs Samus of what has happened on the Bottle Ship. She tells Samus that the Federation was attempting to recreate a special forces unit of bioweapons, based on the heirarchy of the Space Pirates. To that end, the Federation had captured many Space Pirates and created cybernetically enhanced Zebesians to form the core of the force. She explains that "a certain presence" caused the creatures to become ferocious and uncontrollable. Samus assumes that by a "certain presence", she was refering to Ridley. "Madeline" then goes on to say that she sent out a distress signal because she feared the Zebesians would resurrect as real Space Pirates, if left unchecked. Samus finds her statement somewhat questionable, as she doubts whether super-agressive Zebesians would become real Space Pirates. Samus theorizes that without the controling powers of Mother Brain, the Zebesians would become merely a race of feral creatures.
At this point MB leads Samus to a computer terminal, claiming to know of a more dangerous plan. MB explains that the scientists took remnants of DNA found on Samus' Power Suit, which were used to create clones of Metroids and Ridley. Samus asks whether the scientists also created a Mother Brain clone, in order to control the Metroids. MB responds that an artificial intelligence was created instead, which evolved and became self-aware. MB then tells Samus that the Metroids are in a hidden sector called Sector Zero, a recreation of Tourian where Metroids are raised. Samus runs off to destroy the Metroids and MB in the sector, telling "Madeline" to stay hidden. A figure then approaches MB, and she turns to face him before the sound of a gunshot is heard.
Samus heads to Room MW after Sector Zero has been destroyed, where she encounters another survivor. This person claims be Madeline Bergman. Shocked at the strange turn of events, Samus tells her that she already met someone with that name. Madeline reveals that the blonde woman was in fact MB, created to replicate Mother Brain's AI. She was constructed to help regenerate and control the Space Pirate special forces. She originally had an infrastructure after Mother Brain (subsequently resembling Aurora Units as well), but when the scientists got to the point of Metroid creation, she was given a human form to help create a maternal connection to the creatures and successfully control them, inspired by Samus' connection to the Baby. She was dubbed "Melissa" Bergman by Madeline, to help make her feel more human. Madeline also says she felt that Melissa was like a daughter to her.
Madeline explains that MB eventually became corrupt and her personality changed to Mother Brain's as well, and started to go rogue after manifesting emotions, beginning to criticize the work of the scientists. They eventually decided to reprogram her AI, which only worsened the situation. Madeline's presence during her restrainment may have caused the coming personality turn. She takes control of the station, insisting that all humans should be "judged" for their actions. Using her intense brainwaves, she leads all of the bioforms on the ship (excluding Metroids) into killing all the scientists except Madeline, who goes into hiding. Both Madeline and Samus have sympathy towards MB, yet she still hunts them.
After this conversation, MB appears, prepared to attack Madeline and Samus. After Madeline begs her to recall her human side, promising "she'll never fail her again," MB lowers her weapon. She then rushes at Madeline, seemingly pushing her out of the path of an incoming bullet that freezes her. The freeze shot was fired by Galactic Federation soldiers, who run into the room. MB thaws herself and, becoming enraged, summons several Desbrachians to fight off the Galactic Federation soldiers as well as Samus when she tries to intervene, while calling several nearby Ghalmanians and Mighty Griptians for additional reinforcements. Finally, Madeline stops the battle by shooting MB with a Freeze Gun. The soldiers, led by The Colonel, take the opportunity and immediately gun MB down. Melissa is killed and soon afterward Samus is escorted off the ship by Anthony Higgs. As she leaves the Bottle Ship with Madeline and Anthony, images of MB can be seen formed out of space gas while Samus is in deep thought about MB's unfortunate fate; the mentioned images disperse when Samus' gunship passes through it.
During the battle with MB and her four Desbrachians, Melissa must be targeted in order to end the scenario. To do that, the Desbrachians must be shot aside as Samus is defending Madeline in first person view. The Desbrachians must be shot with whatever tool Samus has, in order to stun them.
Character log descriptions
- After RB176 Ferrocrusher attack
- "Seperated from Samus after being attacked by someone."
- After reunion
- "Reunited with Samus in the Bioweapon Research Center, she explained what really happened on the BOTTLE SHIP."
- After credits
- "Shot to death by the Federation."
- MB is the first human android character in the Metroid series. As such, her personality is likely inspired by that of Ash in the film Alien.
- Interestingly, the start of MB's rampage took place mere moments after the Ridley clone (at that time, Little Birdie's) murder of a scientist and subsequent escape. Whether the two incidents are somehow related is unknown.
- It would seem MB's brainwaves as a means of controlling the Metroids are arguably far from perfect. Evidence supporting this is the scientists onboard the Bottle Ship having to create the humanoid form of MB so that the first propagated Metroid would recognize her as its actual mother (since she now resembled a true living organism) and obey her completely. Also in Metroid: Zero Mission and Super Metroid, Metroids had broken loose in Tourian and killed all the Pirate personnel (in Zero Mission) and other species (in Super Metroid), proving that Mother Brain could not control them. In the Super Metroid Comic, it depicts the Baby rejecting Mother Brain as it saw Samus being its true mother.
- Ironically, the antagonist, MB, explained the entire plot behind the Bottle Ship to the protagonist, Samus. Though questionable, it should be noted the fact that she never mentioned the "unfreezable" part behind the Metroids, and as planned, Samus would rush in defenseless against the modified bioweapons and be annihilated, thus, having one less problem for MB to worry about.
- MB's original form, which is a giant, featureless brain floating in a container built by Galactic Federation scientists, shares quite a few similarities with Aurora Units. Though when both constructs are compared with Mother Brain, the AUs only share a similar physiology, while MB not only resembles the Pirate leader (to a closer extent, since MB is more organic), but was also programmed to think like her.
- MB's first form may be an advanced form of Aurora Unit.
- This is not the first portrayal of Mother Brain in human form. In the Captain N: The Game Master comic Nervous Meltdown, Mother Brain's subconscious manifestation of herself was also a blonde woman.
- She first appeared in the E3 2009 trailer, towards the end. Before the game's release, fans speculated she may have been another Samus. Yoshio Sakamoto addressed this issue, saying that she is not another Samus but is a "very, very important character."  Her only other appearance in trailers for the game was in one of three Japanese commercials. Her voice was heard for the first time in said commercial.
- Her hairclip vaguely resembles Metroid nuclei, foreshadowing her connection to the Metroids onboard.
- The hair clip is also the symbol used on the file select menu to show which file has completed the game.
- It is unknown what the fate of the hair clip was, as it fell off of MB's hair during her final moments, and was crushed by The Colonel as he stepped on it. It is absent during subsequent visits to the room, so it may have been that Madeline took it with her.
- The manner of MB's death (being frozen and then killed using projectile weapons) is also similar to the preferred method of dispatching Metroids; ironic given her telepathic link to said creatures.
- MB's body may have been resistant to projectiles unless frozen: when the Deleter; James Pierce; attacks her in the Bioweapon Research Center, a gunshot is heard (presumably directed at the android) and a flattened bullet bounces to the floor.
- It is unknown how MB got the Freeze Gun, but it is likely she took it from James Pierce after she or a Desbrachian killed him. However it could be that the Bottle Ship scientists may also have possessed their own Freeze Guns for use against the resident creatures.
- It is possible that MB 'planned' her own demise, as she clearly throws her Freeze Gun in a manner that allows it to slide between the squad of Federation soldiers and stop next to Madeline Bergman. This allowed Madeline to stop MB's rampage and likely prevented the latter from falling into corrupt Federation hands. She also may have given it to Madeline out of a desperate hope that the scientist would protect her against the Federation.
- The first initials in her name were also the same as the initials for Mother Brain, acting as an early hint at what she truly was.
- Her role in Metroid: Other M is a classic example of an AI going rogue shortly after becoming self-aware, a little like HAL 9000 from 2001: A Space Odyssey, but MB bears more similar characteristics to Skynet (and the titular robots in a similar vein by extension) from the Terminator series, particularly in the sense that she controls the creatures on board the Bottle Ship to be used against humans, and that she herself is an android in a human guise.
- Samus actually refers to MB as "Mother Brain" near the end of the game: "...Mother Brain's rampage."
- In Metroid Prime 2: Echoes, the Quad drone's main body is dubbed as "Quad MB".
- It is strange to note that MB's description in the character log is not altered during her battle. The same happens to Madeline.