The Day family is growing on "New Girl," and the show has cast Linda Cardellini to play Jess' wild sister, Abby.

First rumored during the summer, Cardellini's casting has brought out a few more details about the previously unseen Day sister. Abby is described as something of a troublemaker, and (according to TVGuide.com) Jess (Zooey Deschanel) is going to have to bail the young woman out of a big predicament.

Yes, Jess is the sensible one of the two siblings. That's a scary thought, isn't it?

Cardellini will recur over an unspecified number of "New Girl" Season 3 episodes, with the first one scheduled to air in February. She will then join the rest of the all-star Day clan: Rob Reiner has recurred as Jess' father, while Jamie Lee Curtis guest-starred as Jess Day's mom in the Season 2 Thanksgiving episode.

While recently seen playing Don Draper's neighbor/mistress on "Mad Men,...