Given the grim realities of the harsh world we live in, it would be nice to believe in things like the Cottingley Fairies, wouldn't it? Alas, like most such stories, it was a complete hoax. Although still claiming to have seen actual fairies as young girls, Elsie Wright and Frances Griffiths admitted in a 1983 magazine interview that the famous photographs had been faked. They admitted to copying illustrations of fairies from a popular children's book of the time and then cutting out cardboard figures which they supported with hat pins for the photos they took. It's worth noting that it took the cousins over 60 years to confess, though experts doubted the authenticity of the photos from the beginning.
You might be interested in seeing a couple of movies inspired by the story, both of which came out in 1997. Photographing Fairies is a fantasy romance starring Toby Stephens, Rachel Shelley, Frances Barber and Ben Kingsley. FairyTale: A True Story focuses more on Sir Arthur Conan Doyle, who took an interest in the case due to his keen interest in spirituality and the supernatural. Peter O'Toole plays Conan Doyle and the excellent supporting cast includes Harvey Keitel, Paul McGann and Bill Nighy.