Unfortunately, Christmas is not widely celebrated in Korea. Decorations are scarce, and what little decorations there are are mostly limited to shopping malls. Pictures of Santa or nativity scenes are almost nonexistant. To make it worse, Christmas is widely regarded as a couples holiday, so it is yet another day were "solo" Korean girls mope about their lack of boyfriends.
There is one thing, however, that Koreans do to celebrate Christmas, and that is getting a Christmas cake. Almost every family gets one (and couples get their own, of course, which they then take to enjoy at a love motel, but that's a story for another day), and right up to the holidays, almost every coffee/dessert chain or independent store will advertise their selections of cakes. And in the true Asian fashion, the cakes are decorated very cute or prettily.
The best thing about these cakes, though, is that all the stores are competing to sell the millions of cakes that will be bought. Therefore, all the big chains like Dunkin' Donuts, Baskin Robbins, etc. will throw in free beanies with the cake. It's totally worth it because the cakes range from $15 - $25, and if you were to buy a beanie by itself off a street cart or in the store, they'd cost at least $10. Most beanies average around $18. So basically, you're getting a free cake if you just want the beanies. This may seem silly, but the beanies that come free with the cakes are super cute! I myself bought two cakes just because I wanted the beanies, lol.