I don't know How I really thought of it, I was just cleaning my room and found an old my scene barbie doll. I wanted a project for the day so I decided to make her into a sugar skull, I only came up with the idea to make her into a key chain about half way through making her.
I used acrylic paints, and just attached a keyring to the piece of plastic that held her head on her shoulders lol

I can make a tutorial if anyone wants one :)