She was an ordinary cow who managed to collect every single last 6502 (and derivative) based game console and computer that was publicly sold in the 20th century. After getting her last one she attempted to plug every single thing in at the same time which required a huge number of power strips and outlets and this caused a very high electricity bill but more importantly this caused her to gain superpowers (similar to Nova's "too many toasters" incident) and she can be a cow version of a lot of characters from games for a lot of 6502-based platforms. She is usually a Super Mario Bros 3 cow/raccoon Luigi.
Sample 6502-based systems: NES, SNES, Turbografx16, Commodore 64, Atari 2600 More obscure platforms like the Atari Lynx are totally valid too. Technically her name changes based on what console/computer she's taking from (6502, 6510, 6507, etc) but for simplicity she will just be called Cow 6502, especially since most of the time the system in question will be the NES.
She is playful enemies with Captain Zilog because he promotes Zilog processors instead of 6502-based ones and she lives in Chip City in Toasterland with him. In Chip City, she sells her milk in the form of cheese to snack companies to use on chips because it's especially delicious. Because of this, she has the favor of the Society of Doritos.
Being a citizen in her kingdom, she knows Nova Storm but not very well. When Nova bothers to visit Chip City she usually trades some vials of milk enhanced with squirrel magic in exchange for a bag of special Doritos. Cow 6502 has a strong interest in magic but has no access to any herself.