Lemon appears in the following games:
As the senior scientist and researcher for the Shadow-Mirror faction, Lemon Browning enacts experimentations on artificial, free-thinking life, developing the W-Series, culminating in the creation of the W-Numbers. She cares deeply for her masterpieces, the human-looking W-Numbers, having been given emotions, in order to function flawlessly like humans. Lemon partakes in Vindel Mauser's quest for eternal war because she sees war as a fine testing ground for her theories and creations. Vindel, in turn, allows her much leeway with her experiments, so long as they have applications that further his war effort.
In battle, Lemon is a crack shot, as her Weiss Saver was built for long-range combat. In this respect, she closely resembles Excellen Browning, both being snipers, thereby making them difficult for their opponents to land a hit.
Lemon Browning joins the Shadow-Mirror, becoming the faction's head scientist of weapons research and development. At the same time, she meets new Shadow-Mirror recruit, Axel Almer and begins an informal relationship with him, while rolling out the W-Series bioroids and the W-Numbers, integrating them into the Shadow-Mirror ranks. Lemon sends one particular android of the W-Numbers, W17, ahead into the next dimension the Shadow-Mirror are planning to enter, in order to infiltrate the ranks of the military, leaving them defenseless at the faction's mercy when they finally invade. The story deviates from this point, depending on which protagonist the player chooses in Advance.
If the player chooses the amnesia-strickened Axel Almer, Lemon retrieves him, after Axel self-detonates his unit, refusing to return to the Shadow-Mirror, after allying himself with the Londo Bell. At an undisclosed location, Axel awakes, fully healed from his injuries, with Lemon by his side, attempting to sway him back to the faction by asking if he is willing to disregard "what they had briefly shared". Although Axel is determined to fight against Vindel and his maniacal schemes, Lemon releases him, informing the self-destruct mechanism on his replacement unit is gone and the next time they meet, it will be as enemies.
If the player chooses W17, codenamed Lamia Loveless, Lemon retrieves her, after she self-detonates her unit, refusing to return to the Shadow-Mirror, after allying herself with the Londo Bell. At an undisclosed location, Lamia is repaired and reactivated, with her mistress by her side. Both begin discussing on the topic of free will and the value of being able to make one's decisions, based on their belief of right and wrong. Lemon sees Lamia's allegiance to the Londo Bell as evidence of self-actualization, as if to say Lamia is no longer a mere doll -- living proof Lemon's experimentations with artificial intelligence is a success. She allows Lamia to escape, with her unit repaired, and when Vindel castigates her for it, Lemon simply puts she was overpowered, something that he didn't believe, but let slip past.
In either scenario, Lemon would Axel or Lamia in the final battle between the Londo Bell and the Shadow-Mirror in space, just as the Axis asteroid is about to collide with the Earth, eventually losing her life to the protagonists.
Lemon Browning appears in the prologue, conversing with Axel Almer as to how the transposition is proceeding, with her replying that everything is proceeding as best as possible under the circumstances. The Shadow-Mirror are on the move again, yet a last ditch effort by an Earth Federation Army elite Gespenst squad could throw things off. Without hesitating, Axel orders all remaining soldiers, including Lemon, to enter the portal, while he distracts the enemy. Having entered the Original Generation universe with the rest of the faction, the Shadow-Mirror ally themselves with the Divine Crusader Remnants, providing them with supplies and new machines from their dimension. In the meantime, she sends W17, Lamia Loveless, to infiltrate the Earth Federation Army and search for Helios Olympus. When Axel rejoins the Shadow-Mirror and after briefly engaging the ATX Team, he returns to Lemon, asking if she knows of an Excellen Browning back in their home dimension, as such a person exists in this universe. Upon hearing the name, Lemon appears quite shocked, but shrugs it off momentarily, now fully interested in this Excellen.
When Lamia refuses to return to the Shadow-Mirror on Vindel's order, the events from Advance involving her and Lemon unfold: she is rescued, repaired and released by Lemon back to her comrades, having been convinced the android can make her own decisions. Lemon meets up with Excellen during Operation Plantagenet, questioning on how she had survived that incident, but her moment is cut short, as the Einst mysteriously appear, forcing both sides to retreat. Lemon relocates to the White Star, and makes her last stand, after the Inspectors are defeated. Seeing she will not make it out of this battle alive, she gives Excellen a treat: defeat her in combat, and she will unveil her true identity. Excellen does so, and Lemon's origins are revealed: she is Excellen Browning, but the Excellen in the Shadow-Mirror universe who was killed in a shuttle crash during her youth. Her parents retrieved their daughter's body and successfully resuscitated her, only she was revived as Lemon Browning. In her dying words, Lemon laments that if she had met him in her dimension, perhaps things would have been better for her.
In the prologue portion of the Original Generation 2, in the Shadow-Mirrow dimension, Lemon Browning becomes interested in the Excellence Team's Time Flow Engine and its properties. She requests Axel Almer to retrieve one of their Excellence units and return it to the Shadow-Mirror. However, he would be unsuccessful, due to an untimely appearance of Duminuss. While Lemon is disappointed at not being able to study the engine, she has greater things to deal with, namely the Earth Federation Army catching wind of the faction's scheme, with them ultimately sending their elite Gespenst squad to eliminate the threat. The rest of the story for Original Generation 2 in Original Generations follows the original.
In Original Generation 2, if Excellen lands the final blow on Lemon in the last battle against the Shadow-Mirror inside the White Star, she revises her comment about having children, during the ending dialogue. She tells Kyosuke that she'd like to have twin girls instead, which Kyosuke correctly guess the oldest of the two would be named Lemon and the youngest Alchemie.
Lemon briefly appears in the drama CD of Mugen no Frontier: Super Robot Wars OG Saga, revealing to Lamia her predecessor, W07, before sending her in the first, most unstable batch of the dimension-jumping portal, which eventually leads her to the Mugen no Frontier universe.