I remember as a kid at 5 years old I went trick or treating in a diaper under my costume.
I was wearing a ghost costume and it was hard to remove to use the toilet so my mom had me wear a diaper which I loved.
I wore one of those thick plastic backed pampers.
I then just used the diaper while trick or treating and it felt good.
If a kid or teen is wearing a costume that is hard to get out of then it would always be a good idea to wear a diaper.
I also saw a kid that was 8 years old last Halloween dressed in just a diaper, shirt and shoes and he said he was dressed as Tommy Pickles.
He even had the toy screwdriver in his diaper.
I asked him if he really uses the diaper and he said yes.
He was wearing a size 7 Pampers Cruisers diaper.