Willo the Wisp beech wood in Oxfordshire, near the director's home. Kenneth Williams provided voices for all of the characters. The principal narrator, Willo the Wisp, was a blue, floating creature drawn as a caricature of him, while the name refers to the ghostly light will-o'-the-wisp from folklore. The other main characters were Arthur the caterpillar (as a gruff cockney), Mavis Cruet, a plump, clumsy fairy with an erratic, magic wand, and the principal antagonist, Evil Edna, a witch in the form of a walking, talking television set who could zap people with her aerials. Other characters included Carwash, a snooty bespectacled cat
Mavis Wilton other and [were] great friends, all the way through." Richard Dyer perceives the Mavis and Derek characters to be as "shy physically" as one another, whereas Kathryn Hone, writing in "The Sunday Times", considers Derek "even more dithering than Mavis". Nevertheless the on-screen relationship between the couple progresses quickly, despite the interference of Derek's mother. Actors Thelma Barlow and Peter Baldwin had worked together before their casting as Derek and Mavis, and the two became close friends. Derek and Mavis have been described by "What's on TV" as "an old-fashioned pair who were made for each other", and were typically