Jumanji - Christmas party at the end of the film. Not sure why, but the first Harry Potter film always gives me a festive feel. Bridget Jones's Diary as there are Christmas parties in those. Mean Girls (also doubles as a Halloween film). Apologies for my taste in films 💜

ETA: My husband and I have this childish thing where if we are watching a non Christmas film and a Christmas song plays or there is something Christmassy, like a Christmas tree or anything like that we will say "Christmas film!". This started in one of the Iron Man films years ago when there are Christmas lights and maybe a song playing.