Black and White Halloween Theme: Skeleton stencil. Printable (free) for a costume, but works for a science puzzle too!
DIY Halloween Costumes for Toddlers
Clays outfit - DIY skeleton costume - All you need is freezer paper and white fabric glue.
DIY Last Minute Halloween Costume - Duct Tape Skeleton - Another never mind the kid, I want to do this for me.
Silver Skeleton Costume for Kids from Buycostumes.com