See subjects.
Reference:
Dogs and other animals celebrating their birthday.
Doesn’t exist in France, as far as I can tell (even though I wouldn’t be surprised if it had been “imported” recently).
Here in the UK it is more common to see paper “crowns” like this (well, usually less elaborate plain tissue paper ones) at birthday parties, although they are also a Christmas thing.
Same for Germany - did not exist in my childhood; my nieces’ birthday parties did not have them; a Google image search for Kindergeburtstag shows some few photos with these cone-shaped hats but I wonder if these are stock photos of US origin. Might have been imported to some extent lately, same as with Hallowe’en.
Are they all that common, in real life, even in America?
I would say birthday hats are not super common, but common enough that if a kid went to birthday parties for all his class, they would be seen several times in the year. (However, It’s been quite some time I’ve been to a kid’s birthday party). But if you do see hats, you see the cones. The birthday child himself may were a fancier version or perhaps a crown. I assume the origin is that they are incredibly easy and cheap to manufacture
Not super-common, but still part of a well-appointed birthday party as promoted by Party City outlets and the like :D.
The cone hat seems to have a lot in common with the kind of hat Pinocchio wears in the original Carlo Collodi novel (and also as rendered in Roberto Benigni’s live-action Pinocchio [2002]). I don’t think the birthday hat started with Collodi’s book, but the general cone hat does seem to have a history in some part of Europe.
Also, stackable, but I think they are supposed to look like circus clown hats, because I remember when I was really little, sometimes a pack of party hats had a crown for the birthday kid, pointy hats with ruffles around the bottom, but other sorts of hats slightly reminiscent of various types of clown hats-- you know, slightly misproportioned top hats and bowlers, and a couple of pirate hats. The deluxe package had things like paper flowers and other trimmings to glue or tape onto the hats.
One year, at one of my cousin’s birthdays, my uncle made everybody hats by folding the wrapping paper from the gifts. Most of the hats were the upside down boat type, but he could make a couple of others, and he put some staples in the to hold them together. Some people wanted the conical ones, I guess because it was the classic.
So, they serve a dual purpose. They are both conical and comical. 
Just saw wiki Pointed Hat. (I had thought of 15th century Renaissance ladies, and of the Jewish Hat, both of which are common in contemporary paintings. (The Yellow Star wasn’t an option; the hexagram wasn’t a Jewish thing then.)
Xref to Party Hat. Xref to Birthday Party.
No joy. Light an offering to Cecil?
They’re party hats, not birthday hats. I’ve seen them at birthday parties, but also at Christmas, Valentine’s Day, New Year’s and other events. Usually at parties with or for children, but I did see lots of people wearing them at New Year’s dances during my band days.
Pointed paper hats used to be common in the UK at least until around the 50s/60s (I remember them from childhood). Now, as said above, the paper crown seems to be the norm.
Exactly. I don’t associate them with birthdays so much as party celebrations in general. There are an occasional thing to add an a light-hearted atmosphere to the party. I remember seeing these going back to the 1960’s.
(“Party hats” is also a slang for when it’s chilly and a woman’s nipples are quite visible pushing their shirt out - based on the cardboard cones, I presume. )
And economical.
Without costing astronomical.
I haven’t been to a children’s birthday party in a long time, but I would have thought they were nearly universal at such. I’m surprised to see people saying they’re “not super common.” Certainly any store in the US with any themed birthday-party supplies whatsoever would have conical hats.
OTOH, I don’t think they are common at any other celebrations, with the exception of New Year’s Eve, where they take their place among other types of hats, masks, and novelty fake eye glasses. I’m sure you can get Christmas or Valentine’s Day themed ones, but I wouldn’t expect them the way I expect to see them at a children’s birthday party.
BTW, I think it is fascinating that our society has a special ceremonial headgear whose only purpose is to be worn at birthday parties, and which is only worn at birthday parties because of tradition. They don’t serve any benefit or purpose whatsoever; they aren’t even particularly fun or creative (like some of the more elaborate novelties associated with New Year’s Eve or Halloween). Yet virtually everyone in our culture has worn one before and most will gladly wear one again if they are at the appropriate event. Why? Because that’s what you do. If Obama attended a children’s birthday party, he’s wear a cheap cardboard cone on his head. If a homeless shelter throws a party for a homeless kid (or even adult) there’s a better than decent chance they’ll spend money on cardboard head cones. What else in this society is so universal and yet so purely ceremonial?
Yet so quintessentially American:)
This is likely to be the reason they’re used as party hats. They just don’t cost very much.
At a relative’s 7th birthday party this past Sunday. The young 'uns had the cone hats. I’m at the age where all my peers have kids between 0 and 13, and I am at far more kiddie parties than I would like. I would say I see the pointy hats at about 10% of the parties.
Common enough that nobody’s surprised to see them, but not universal probably because most parents don’t think they’re worth the trouble.