So-called crop cirles are my favorite hoax. Two jokers in the 1970s read about a UFO report in Australia, in which the gentleman reporting the UFO said he had found a "saucer nest" impression in some swamp grasses. So, with some very simple tools, they began making crop circles. In about 1990, they revealed their hoax to journalists, and made a crop circle while the journalists filmed it. A prominent "cereologist," i.e., someone who studies crop circles, was brought in, and declared it authentic. Bower and Chorley had used a simple, inexpensive, collapsible painters' scaffold to get into the fields without leaving tracks.
I saw a television program about this, and some new age types at Stonehenge for the solstice were asked about crop circles, and they just jumped all over it. Then the television crew showed them video of Bower and Chorley making a crop circle. Most of the hippies quicly drifted away, others said, basically, yeah maybe, but that doesn't a count for all of them.
Since that time, "cereologists" have frantically hunted up "historical" references to crop circles. If people want to believe such a thing, nothing will dissuade them, not even the evidence of the people who have perpetrated the hoax. I feel sorry for the unoffending farmers.