As a child i lived with my grandad
My mother was a sucker for a freebie (she'd spend £20 just to get a £1 freebie) and around the time I was about 7/8 ish she started buying these flower fairy dolls and collected the tokens so she could send off for a small purple box for teeth
It arrived,got shoved in a drawer and finally a tooth fell out
I popped it in my box and put that under my pillow
Woke up the following day and there was my shiny coin but the tooth was still in the box
I asked grandad why the tooth fairy hasn't taken it with her and he told me the tooth fairy had arthritis in her fingers and couldn't open it
I was a LOT older when the penny dropped it wasn't the bloody tooth fairy that had arthritis!
He also convinced me that when I left the room,my toys would run around the room and race back when they heard me coming no matter how quiet I was (and believe me,I tried!)
I was a very gullible child