|Common name||Darwin OS|
|First appearance||Dec 2006|
|Height||137 cm (4'6")|
|Weapon(s)||guns borrowed from NeXTSTEP-tan.|
|Faction||Wanderer Class, honorary member of the House Of Mac|
|System personified||Darwin OS, the kernel of Mac OSX|
|Debut||16 Mar 1999|
|Latest release||v.9.x (still maintained)|
Darwin OS-tan is represented as a small girl with green eyes, and short, wavy blonde pigtails in a similar style as NeXTSTEP-tan's. Her outfits are mainly in white with black decorations, are lightweight and practical for adventuring in. She is accompanied by a horned platypus (Darwin's mascot) which she keeps as a pet, and she often accompanies NeXTSTEP-tan when adventuring, or Rhapsody-tan when at the Mac House.
One of her endeavors is collecting and cataloging bugs. Referencing her namesake, she also studies evolutionary biology.
Her resemblance to NeXTSTEP-tan and Mac-tan/Mac OSX-tan is because she is the 'missing link' between the two OSes. She is Mac OSX Server-tan's first daughter, is the older sister of the OSX-tans and younger stepsister to the Classic Mac-tans. Darwin OS-tan loves all of her relatives of the Apple Family but is mainly seen accompanying NeXTSTEP-tan or one Mac OSX-tans.