Ark received AIR at her assigning. At the time, she was a regular SIR Unit, and Ark knew that would never do. She took AIR back to her lab, where she modified and customized her. AIR serves alongside her, and is her best friend.
AIR is very similar in personality to Ark. She is incredibly loyal, but will only listen to Ark. If, say, Zim were to command her, she would blast him into a million pieces with her cannon.
AIR is very small for a SIR Unit. She has light ailver metal, gray eyes, pointed shoulders with the Irken symbol on them, black stripes winding around her, three-fingered hands, and more weapons packed inside of her than you could ever imagine.
Invader Ark- AIR loves having Ark as a master, and respects her greatly.
GIR- AIR thinks GIR is a little bit stupid, but also thinks he's very funny. She likes him more than she is willing to admit.
Vira- AIR likes Vira, and will do anything for her if Ark tells her to.
Comatose- AIR also likes Comatose, and will do the same as she will for Vira.
Fury- Fury is a great friend of AIR's, and they operate well together.
SO- AIR and SO are best friends.