The idea behind the witches is in the classic "three witches" coven idea, popularized (if that's even the right word) by Shakespeare in Macbeth - featuring the Crone, the Motherly one and the Maiden characters.

This has been reused over and over again, and my particular inspiration behind these witches is in the coven of Granny Weatherwax - a prominent character in Terry Pratchett's Discworld series - a set of books known for lampooning everyday life in fantasy environments and exploring the idea of beliefs and folklore.

In mine, the crone is really generic - like all the traditional Hallowe'en masks, the mother is a sweet, gentle type (whose looks I based off Dawn French) and the Maiden who is a girl who thought she was going to be joining a satanic wiccan cult (which we all know is a load of nonsense)