it's some sort of UK/commonwealth thing. Go reread Harry Potter and the Sorcerer's Stone. They have some in there. hats, stuff, fireworks toys. idk
I did, I don't remember anything like that.
It's very low-key. The Weasley twins frog-marching Percy down to the Great Hall in his new Weasley sweater, dumbledore gets a bonnet out of his cracker, which he wears, etc. I guess it could be in any of the first three, though