Zia spends much of her time plugged into the Ultranet, and in doing so somewhat disappoints her mother. Zia looks most like her mother, explained to have most of Lisa's genes. However, Zia is much more rebellious than Lisa, which leads Lisa to think that Zia doesn't respect her. She has a changing tattoo on her left arm, one of which is the Taoist symbol the Yin Yang.
Worried, Lisa enters the Ultranet to check up on Zia despite her own feelings. It was there Lisa learns Zia looks up to her more often than Lisa thinks. Lisa tells Zia that she's sorry for invading her privacy and promises to be less naggy. A door to another room, a dance club, opens slightly, so Zia closes the door before her mom realizes what's behind the door.
Zia's last name is highly disputable. It is heavily implied that Lisa takes Milhouse's surname. However, Zia's Ultranet Room reads on the front "Zia Simpson". One reason could be because Zia has a better relationship with her mother (Lisa Simpson) than her father (Milhouse Van Houten).
Zia has a tattoo on her upper left arm that is evidently a hologram or some other similar device, since it changes into several different designs. These designs include: