A friend told me that in her street a pumpkin outside the house indicates the houses that play the trick or treat game, and most do. She invited us over to join the gang that meet at her house and knock on doors for sweets.
This is what the children looked like before they left the house:
This was Hannah towards the end of the evening:
She'd been chewing the top of her witches hat and the dye had stuck fast to her mouth and hands. Whilst the dye clearly wasn't fixed to the hat, it did seem to be permanently fixed to her skin. I haven't resorted to bleach or Brillo pads, yet.