Ruby was originally part of a gang of street Meowths, who lived off of garbage and refuse and avoided the human world. Her gang was lead by Tsume, a strong, forceful Meowth who protected them from Humans. Ruby, however, always wanted to have a rich, happy life, where she would be pampered, and felt that she was a princess born into the wrong body. Tsume told her she was stupid for this, as did almost all the other Meowths she knew, but she didn't care. She believed that she had the right to choose and live the way she wanted. She also believed that she personally was the most beautiful thing alive.

After hearing the warning call of "Human!" for the last time, Ruby decided to see just who this human was. Finding a cruel boy with one of her instinctual enemy Pokémon, a Growlithe, she decided to toy with him. Sauntering just out of reach and defeating all his Pokémon, Ruby taunted the boy into following her, then buried him in a pile of boxes she knocked over.

Returning to her friends, Ruby found Tsume battling with the Growlithe and found something rising in her chest. Perhaps the Growlithe had ignited it, but she didn't want her friends to be hurt for this and wasn't going to let them. With a surge of energy, she leapt forward to attack, burying her claws in the Growlithe who bucked back and forth. Crashing into a pile of boxes, it knocked a small metal box down onto Ruby's head, causing a strange feeling to come over her. Little did she know that the box was a TM, and the feeling was the knowledge of Thunder. She employed this knowledge and defeated the Growlithe easily. Checking that Tsume, who had been knocked unconscious, was okay, Ruby limped her way out of the alley, confused and tired from her exertion.

This was how Radic found her.

After cleaning her up, Radic asked her if she would like to join him, and seeing that he was the type that would fully pamper her, she agreed, but then found that the other Pokémon she had to deal with were not quite so genial. Kitsune instantly attacked her for her heritage and Nova's arrogance put her on edge, not only because he thought he was better than her, but because he was her instinctual prey, a rat, and he thought he was better then her. Thus began the long rivalry between the three. Ruby didn't get along with many in her group, because her ego soon reached monstrous proportions.

While walking once, Radic encountered another trainer who asked to battle. Shrugging, Radic agreed. Radic won every battle until they finally began to release Pokémon at the same time.

Ruby found herself facing Tsume, evolved and weakened beyond recognition. The fire that Ruby had once admired had died in Tsume's eyes, and this infuriated her. The Meowth, however, didn't have the speed or the power of her evolved form and she was losing. It wasn't until Tsume attacked and injured Ruby's face that Ruby finally was able to look past Tsume, her friend, to Tsume, her enemy. With a cry of rage at the destruction of her beauty, she sent a raging strike of Thunder at Tsume's trainer.

After he passed out, she begged Tsume not to let him kill her spirit, and she told her not to worry. After Tsume walked away, leaving her trainer behind, Ruby found herself evolving.

Ruby doesn't trust people easily and doesn't like those who make fun of her. She's buried her past completely, refusing to believe what her life used to be, and believes her fantasy of truly being a princess. She often demands that Radic lavish attention on her, which he does. She is very loyal to him for that, although she pays no attention to him in battle. She trusts her own judgement. She cares for Radic and will fight for him if he is threatened. She hates Growlithe or Arcanine and considers smaller, rodent-like Pokémon to be her prey. She can be extremely vicious if angered.