Eliot liked his reputation. He had done his best to earn it, and then keep it intact. If he could avoid it he didn't twitch (unless it served a purpose), he didn't show much emotions when he was playing the part of retrieval specialist. His occasional singing he allowed himself, all that bend up emotion hadto go somewhere.
Christmas song's were definitely a serious threat to his bad ass, no non-sense rep. And he disliked those occasionally catchy pieces of "music" for it. They made him suddenly notice he was nodding his head to a music only he could hear – and that wasn't at all cool. So, every year when Christmas started to near again, Eliot picked a new song for him to humm in his head every time a Christmas carol started. (He was not going to be caught nodding his head along with Jingle Bells – ever again.)
This year he had made a mistake, though, one he swore he was never falling again. Somehow Eliot had lost a bet to Parker, and she had gotten to be the one to choose this years song. Eliot swore she cheated – she always does! – but he didn't know how or when, so he had to acquiesce to the validity of the bet. That'd be why he was scowling harder than any of the previous years when ever a Christmas song could be heard.
The only positive side to it was that it's rather amusing watch grown men get a scared looks to their faces when he started, in a near growl, recite under his breath "I don't know who you think you are, but before the night is through, I wanna do bad things with you. I wanna do real bad things with you."