Back in 1998, when the UK moved its celebration of the newly-created World Book Day to early March, so that it wouldn't clash with Easter, it was a fun thing. There were £1 book tokens given to every school pupil, a limited selection of £1 books were stocked for the spending of said tokens, and in an effort to promote the whole idea of reading books, some (and I emphasise the *some* here) schools allowed the children to dress as a character from a book for the day. And some of the kids did, utilising things they had in the house already.
I was teaching a Year 4 class at the time (eight year olds, for those unfamiliar) and was known to be heavily into books. So although I'm not generally one for dressing up, I did on this occasion. Black trousers with a tail safety-pinned to the back, a black top, some cardboard ears attached to a hairband, whiskers drawn on with an eye-crayon - and of course, a cardboard box so that whenever anyone looked in my direction, I could put it over my head since I was the cat from My Cat Likes to Hide in Boxes. I think the whole outfit involved an outlay of about £2, for the hairband.
Now it seems to be obligatory that not only the pupils but also the staff dress up. Some start preparing weeks beforehand (I know at least one mum who did). Judging by the photos on Facebook, quite a few are costumes either hired or purchased - I suspect the supermarkets do their best to encourage that avenue. One student teacher I know spent Wednesday evening making a costume out of cardboard and tape so that she could dress up for her Year 1 (five year olds) the following day. (She had talked about buying some props beforehand, but being a student teacher, she's on a budget and overworked).
I'm all in favour of encouraging reading. Giving the schools some support when they are struggling with funding for the basics is also to be encouraged. But to put pressure on schools and families to spend time and often quite a lot of money is not acceptable. Peer pressure can be toxic, so the optional nature of the thing has to come from the school's leadership team. Teachers can lead by example - they are supposed to model acceptable behaviours, so this could be just one more.
And I really hope that one meme I saw on Facebook isn't true - that some families spend more on costumes for World Book Day than they spend on books in a year.