Hexadecimal is an insane virus operating out of Lost Angles and who has a not-so-secret crush on Bob. She constantly wears a mask, changing them through waving her hand in front of her face or turning around so the viewer never really sees her change masks. In all practicalities, her vast collection of masks shows her facial expression (thereby giving her a harlequin-like appearance). The expressions shown in these masks range from happy, scheming, to a downright homicidally insane expression. These masks also hold her power in check, though when removed (as in the episode “Painted Windows”), her power escapes and continues to do damage although she will overload and be destroyed if the mask is not replaced. Hexadecimal has the ability to control nulls (sprites downgraded to slug-like status for losing to the User in a game), which has earned her the title “Queen of the Nulls.” Hex has transfinite power – meaning that, though her power is not infinite it continues to regenerate even as she exhausts her power; Hex can be weakened and takes time to restore herself to full power, but she will return to full power.
Both Megabyte and Hexadecimal were at one point part of the larger virus Gigabyte. It was accidentally split into two effectively opposite parts, Megabyte representing order and Hexadecimal representing chaos.
She is a benign virus, meaning she doesn’t infect other entities. Instead, her whole motive was to cause random chaos for fun (and also to kill Megabyte, who kept trying to kill her, possibly due to sibling rivalry). Due to her power and insanity, her fun nearly always led to Mainframe crashing. She even once nearly caused it by accident, when a Web Creature possessed her and the nulls formed a giant “Nullzilla” around her as a result.
Her power charged the Hardware that closed the portal to the Web in Web World Wars, but on a whim she decided to fire the Hardware at the Principal Office, which would destroy the Core and the whole System. Luckily, a Game Cube landed on top the Hardware and the feedback from the Cube along with the charge that she had already built up in the hardware seriously damaged her; Megabyte had her rebuilt (which, thanks to Bunnyfoot, was in bondage gear) and enslaved her into being a weapon he could use against Mainframe. This only made her more insane and very angry, and when she broke free of Megabyte’s control her resulting rampage devastated G-Prime. She spent the rest of her days lurking in Lost Angles (a play on the word Los Angeles), until a returning Bob was able to defragment her – her masks were replaced by a real face (it looked exactly like her masks, except her mouth moved to her voice) and her insanity was replaced with quirkiness.
When Mainframe restarted, a viral scan disinfected all the Virals in Mainframe. Hex, who had been given an Icon (or PID) and registered with the Office at Bob’s insistence, was scanned but was so powerful that she wasn’t disinfected. When her power was lessened in Daemon Rising, the viral scan (which remained in her Icon) started again and turned her into a normal unpowered Sprite, wearing white and gold instead of red and black. When Daemon conquered Mainframe and Bob was in danger of dying, Hexadecimal absorbed some of Mainframe’s core energy in order to become the Hexadecimal of old once more, now with power levels comparable to even Daemon’s. She finally had to sacrifice herself by spreading her benign infection (which contained the cure to Daemon’s infection) throughout the Net.
Her name is a reference to hexadecimal notation, which programmers sometimes use rather than binary notation.