Some God-types do and some don't celebrate Chrismahannakwanzafestistice in-game, but accuracy and common sense have never stopped us from memeing before. So! Pretend we live in a world where there is some kind of social pressure to give gifts to lots of people on the same day. Then:
1. Have your characters post 2. Other players will reply telling you what their characters would get yours 3. You do the same for them
Obviously not everyone would get presents from everyone else, but they don't have to only get imaginary gifts for the people they like. Hate-presents are also encouraged.