AceShowbiz -

FOX has determined which "Bones" episode the Deschanel sisters should appear together in. Through a press release, the network announced that Emily Deschanel and Zooey Deschanel will do a sister act on the December 10 episode called "The Goop on the Girl". It will be a special holiday-themed episode which is also guest starring Farrah Fawcett's widower Ryan O'Neal.

Zooey's role on the show would be a distant relative of Emily's Dr. Temperance Brennan named Margaret Whitesell. O'Neal, meanwhile, reprises his role as Max Keenan, Brennan's dad. When Keenan makes contact with Margaret, he invites her to spend Christmas with him and his daughter. Meanwhile, Brennan and Booth investigate the death of a man dressed as Santa Claus who was blown up after a botched bank robbery.

Zooey Deschanel takes more feature film projects than her sister. She made a starring role in "The Assassination of Jesse James by the Coward Robert Ford" and most recently, "500 Days of Summer". She is also a recurring role on "Weeds" as the free-spirited Kat.

In the press release, FOX also announced that the 100th episode of the show will be directed by David Boreanaz. It will air in Spring 2010.