Despite Christmas being a cultural holiday in Finland, Moomin family is rarely seen celebrating it. This is because Moomins and most of inhabitants in Moominvalley go to hibernation in November and wake up in Spring. They have encountered this holiday in many versions, often with hilarious results.
In the books, Moomin family first learns of Christmas in Tales from Moominvalley when a busybody neighbour wakes them up because Christmas is coming and they are not prepared. Moomin family observes the panic around them and comes to the logical conclusion that Christmas must be a scary monster. Rest of the short story is spent preparing to ward off this horrible beast with offerings. Eventually they go to sleep because the monster does not appear, leaving small creatures to enjoy their unconventional Christmas banquet.
This plot is often used in animated adaptations. Famous 1990s Japanese animated series used the short story as basis for episode 36 - Christmas is coming. Later Season 2; Delightful Moomin Family Adventure Diary, has Moomin family already familiar with Christmas traditions but they do not seem to make effort to remember it until Moominpappa’s aunt points it out.
Comics had some fun with Christmas from time to time. Because some plots demanded that Moomin family stays awake for winter, it soon became a running gag that they will always be interrupted. This reached a point where Moominmamma tries to lure in guests in the winter with coffee because she feels weird about having a peaceful winter. This means Moomins got to celebrate Christmas few times but the results are often filled with Lars Jansson’s typical humoristic touch.
Merry Christmas! Happy Holidays! And if you are like Moomins, feel free to skip celebrations and go straight back to comfortable hibernation.