I just got off KL644 from JFK in J so I can't say anything about Champagne in Y or W but I can say that the crew had put up decorations at the boarding door, were wearing festive hats (and some the KL Christmas sweater) and one of the crew thought to bring a couple of oliebollen:



Another crew member serving me breakfast was rather surprised at me eating this so it seems to have been the work of one of them showing some initiative which, big thumbs up. I don't believe there was an announcement at midnight but to be fair the flight departed at 21:30 so almost everyone would've been sleeping or trying to.