Mac OS X-Tan
The Mac OS X girl is often portrayed as cat-eared, following with the Apple "wild cat" naming tradition. (Every Mac OS X release has a codename like "Jaguar", "Panther" and so on.) Otherwise, she is shown as an older variation of the Mac OS 9 girl, wearing a platinum white coat and a wireless AirPort device fashioned as a hat. She is occasionally shown holding a publication of some sort, as Macs are often used for desktop publishing.
Mac OS 9-Tan
Mac OS 9 is the most common Mac OS girl. She is blonde, and wears a ribbon shaped like a 9 and a "platinum white" bodysuit. She usually carries a large apple on her head, or a bomb from the standard Macintosh error dialog. Other common accessories are a white dress with the Mac face logo on the skirt with a slit up the front that follows the nose/profile line, and showing some of her hair like the "detached leaf" as used by the multi-coloured Apple Computer logo. Usually friendly and demure, OS 9 has been known to fly into insane rages when angered.