I guess this is funnier if you have seen Community and know how wonderfully innocent and naîve Alison Brie's character Annie is.
... Unfortunately I couldn't find the whole clip of the xmas-costume dance from which there's a couple of seconds at the end here, for it's one of the sexiest things I've seen, prob the hottest xmas song since Eartha Kitt.
I don't know where this is from, but she's very funny like usual:
She really is beautiful. Watch Craig Furguson here, he's so overwhelmed he has to scoot away from her!
Quote from the show:
"There will always be a reason not to follow your dreams."
That's great. And it's useful for going either way!