Note: I know it seems out of character that Brennan would give Booth such a gift, but let's just say that even if pop culture isn't her thing, she does research.

The day after Christmas, they find human remains in a slaughterhouse and for that time both stop thinking about mistletoe and trees and Vermont.

Later, at the diner, she slides a box across the table and he raises an eyebrow.

"What happened to a holiday dedicated to self-promotion?"

"Well, if it's an exchange of goodwill and-" she catches him smirking "- I thought you knew all the rules!"

"There don't have to be rules for everything, Bones. Christmas is different."

Different strikes a chord with her, and he can't help but grin when he unwraps a pair of Grinch socks.