White Baby is a new unit introduced in Metal Slug Attack.
White Baby is an AI that takes on the appearance of a young girl. She likes playing with toys, having created the Valerian Bears for this purpose. She also acts on her own needs. Amadeus sees her as one of his children despite her disobedience towards him.
She makes her first appearance in "Protection of the Fortress" where she teases around with her younger sister Iron Fortress before heading out. She battles Allen O'Neil in his new Sergeant Drill, but is quickly overwhelmed. Iron Fortress defeats Allen and brings White Baby back to headquarters to allow Amadeus to fix her.
Later on in "Sky King", she frees her older sister First Baby and the two run around causing havoc. Navy tries to hack First Baby, but White Baby quickly intervenes and removes Navy's program from First Baby before it is able to fully control her.
Due to attempting to absorb Sol Dae Rokker Anima, White Baby becomes corrupted by the immense power it contained. She returns to headquarters, getting her siblings' attention as they are unable to understand what she is saying. White Baby confronts a Golden Turtle, sent by Towa and destroys it. The power that corrupted her is dispelled in the battle, and she does not recall the battle she just had.
Later on, she paints the Iron Fortress (and Valerian Bear Rosa) gold, much to the former's horror. She watches as the enemies chase her younger sibling, giggling throughout the fight.
White Baby later accompanies the Iron Fortress with a group of Amadeus robots as they are ambushed by SV-001s led by MS-Heart. White Baby destroys or immobilizes most of the enemy, but is soon surrounded by Heart and her remaining forces. She uses her hacking powers to control Heart, but becomes disappointed when she tells her she relinquished command of the tanks to prevent her from gaining information. Though disappointed by the setback, she continues hacking and manages to make her self-aware, watching as Tarma arrives before Heart drags him away from the scene.
First appearing in "Guilty Child", White Baby tries to ambush Abigail and Allen O'Neil who were overseeing a negotiation trade between the Rebel Army and Amadeus Syndicate. They easily break her "toys" and she becomes more interested in them. When the two officers finally arrive at an Amadeus facility, White Baby forces her creator onto the Mother Computer to fight them one last time. After they defeat the Mother Computer, she flees, promising to find better "toys" for them.
Later on in "Cross/You", she hacks into the Amadeus Syndicate again, who are trying to revive the destroyed Sol Dae Rokker (which was a result of the Professor's actions). Amadeus states that he didn't create her to destroy, but she points out that he made her to control the weak. Amadeus states that there are others stronger than her, which gets her attention. When Navy arrives with Vita, White Baby notes Vita's mechanized appearance and asks why she is with a human. Upon Anima's defeat, she runs off.
In "Cyberbrain Friend", White Baby takes the alias "Ms. White" and talks with MS-Alice about the concept of friendship. She also sends robots to attack an Regular Army base in order to get her attention. Like with Vita, White Baby is surprised that MS-Alice is with a human and wants to learn the concepts from her. Upon its destruction, White Baby hacks into MS-Alice to learn about her past. When MS-Alice regains consciousness White Baby apologizes for her intrusion and promises to let MS-Alice look inside her in the future. She later talks with MS-Alice in a private chatroom, as the two AI have considered themselves friends.