Holiday song is definitely Santa Baby, except Harry changes it to "Santa's Baby...Hasn't been put under the tree, poor me. I'm fine with boys or with girls. Santa's baby still hasn't been adopted tonight." And Louis just pinches the bridge of his nose and nods. It's still more subtle than the time Harry left out his Christmas list and it was nothing but baby things with "but I need the baby first" next to each one. He gets Harry a baby doll as a joke and gets kicked out of of bed.
OMG. NOOOOOOOO NO NO NO NON IOOOOOOOOO HARRY WANTS A BABY.