I have a history of putting stuff in my diaper, when I was a toddler I would store candy in the waist band or even in my diaper (if it was clean) along with sometimes putting toys in them because in the 90's Rugrats was popular and I imitated tommy as much as I could, wandering away from grown ups and going on adventures and putting toys mainly a set of plastic car keys in the front of my diaper instead of a screwdriver.
When I was 6 and had to wear diapers because of medication I was taking and we spent weekends down at a campground I would put a bill fold with some money in the waist band or if I was doubled diapered in the outer diaper.
When I had to wear diapers at night for bedwetting I would stuff plain white night t-shirts down the back of the diapers acting as if they were really thick and now I might pour some water in the front and back of my diaper to get it to swell so it's nice and thick and squishy.