|My concession to Halloween
This is called "beating the cat out of the barrel" and legend has it that there once used to be an actual dead cat inside the barrel. It is actually quite a Halloween-like tradition if you think about it.
Later, when I went away to boarding school in Akureyri, I became familiar with the tradition of dressing up and going singing from door to door in the shopping district to get candy on Ash Wednesday, sort of like trick-or-treating in the USA, only with singing and no trickery.
I think, although I can't be absolutely sure, it was Hard Rock Café that introduced Halloween to Icelanders, although we of course were familiar with it from American movies and TV series. There was a Hard Rock Cafe here in the 1990s (it closed in the early noughties, I think, but a new one will be opening soon), and every Halloween they would promise a free meal (or maybe it was a drink - I can't quite remember) to anyone who came in to dine wearing a costume on Halloween.
Then shopkeepers realised that here was a chance to sell stuff, and it took off - sort of. You can now buy large pumpkins for carving, and Halloween decorations are available in many shops, and you can spot the occasional adult wearing a costume in public on Halloween, although it is, in fact, mostly celebrated by kids, who love an excuse to wear costumes and have school costume parties.
Trick-or-treating (without actual tricks) also happens, albeit on a more limited scale than on Ash Wednesday, usually with certain neighbourhoods deciding to participate and participating homes marked with balloon.
There is no religious aspect to Halloween in Iceland, as most of us are Protestants of some kind and the religious aspects are too Catholic for us, and we observe it purely as a secular celebration.
It's still much more common for kids in Iceland to dress up for Ash Wednesday than for Halloween, but it is becoming more common and I expect it will continue to grow in popularity. The most noticeable difference between the two celebrations is the horror aspect of Halloween. You don't see many mummies, zombies, witches and skeletons on Ash Wednesday, but there is a proliferation of them on Halloween, along with fake blood, carved pumpkins and other necessary accoutrements.
I see no harm in celebrating Halloween - any excuse to have a bit of fun at this time of the year is a good one - but I dearly hope that Halloween does not destroy the old Ash Wednesday tradition.