""Merry Christmas, idiot." Arms fall around his friend's waist from behind, a grin and a light kiss pressed against his ear. "Know what I got you? A flarking day off. Everyone else's dealing with shit after I explained them it's a terran holiday. Also possibly something else, but that's for later." "
He tries (and fails) to mask his surprise, both at the sudden presence at his back and the fact that it is Christmas Day. It’s not something that he actually remembered, that it is Christmas as it were, (he remembered not holidays or birthdays, even his own; though it wasn’t that he didn’t exactly remember the dates of them but when the dates actually came near), for days blur into each other too often, and he had better things to do.
So, yes it definitely caught him unaware when Pete wished him a Merry Christmas; and subsequently takes him slightly long to reply.
“Can’t remind the last time I celebrated it…
Merry Christmas, Pete.”