I believe you are looking for season 5 episode 10, The Goop on the Girl. It aired in the US on December 10, 2009. The following is the wikipedia description:
When a man dressed as Santa Claus blows himself up during a botched bank robbery, Brennan and Booth work to identify the bomber and determine his motives. Meanwhile, Brennan makes plans to spend Christmas in El Salvador, but her father (guest star Ryan O'Neal) convinces her to spend the holidays with him and Margaret Whitesell (guest star Zooey Deschanel), a newly discovered distant relative.
December 16, 2010 aired a repeat episode of Bones as they are on hiatus until January 2011.
Hope this helps you out and have a great day!
I'm guessing it's the episode Bones Season 3 Episode 9 The Santa in the Slush.
Its called "The Goop on the Girl" season 5 episode 10
http://imdb.com/title/tt1541172/
