Zooey Deschanel, Emily Deschanel Zooey Deschanel, Emily Deschanel

Zooey Deschanel ((500) Days of Summer) has signed on to guest-star on an episode of Bones alongside her sister Emily Deschanel.

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In the first-ever on-screen pairing of the Deschanel sisters, Zooey will play Margaret Whitesell, a distant relative of Emily's Dr. Temperance Brennan. Brennan's father, Max Keenan (guest star Ryan O'Neal), invites Margaret to spend Christmas with him and his daughter.

In the same episode, Brennan and Booth will investigate the death of a man wearing a Santa Claus suit who dies in an explosion at a botched bank robbery.

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The sisters' holiday-themed episode will air in December.

Are you excited to see Zooey and Emily — together at last?