They used to be one of the planet's great unsolved mysteries of our time. Explanations of who or what made them ranged from aliens to freak weather.
But when it was admitted they were hoaxes 15 years ago, there was dogged disbelief among those who looked for paranormal answers – and today there is a growing number of people who still think that not all crop circles are man-made.
A vast picture of a pig was done as a publicity stunt aimed at maximum exposure alongside the M11 in Cambridgeshire.
What the circle makers probably didn't realise was that they were tapping into a rich tradition of crop formations appearing in this region.
While crop circle researcher Hugh Newman accepts that circles can be man-made, he is scathing about those who cheapen the mythology.
"I have no problem with man-made crop circles, but there have been stories about people who have made crop circles and tried to fool the researchers or ridicule them," he said.
"It just brings an element of deceit and lies and I think there is no need for that."
Hugh is unshaken in his belief that human consciousness and earth mysteries account for a great number of formations.
He cites an amateur video called The Oliver’s Castle Footage as proof of a supernatural involvement.
In 1991 a unique crop formation appeared in a Cambridgeshire field. Called the Mandelbrot Set, it turned the whole enigma on its head.
Based on a set of geometrical patterns discovered by mathematician Benoit Mandelbrot, it was so complex it reinforced the belief it couldn’t have been made by human hand.
Inside Out decided to see if it was possible to recreate the Mandelbrot Set in a field of crops in Norfolk at night with no lights. And with the farmer’s permission, of course.
Circle makers John Lundberg and Rob Irving took up the challenge.
In just over four hours and in the pouring rain, John and Rob achieved the impossible: a complex structure several hundred feet deep in the wheat.
And before they slipped away quietly, there was one more revelation up their sleeves. In relation to the Oliver's Castle amateur footage, John Lundberg said, "It's a fair cop. We did it."
The field in which the crop circle was built was harvested the following day - and all traces of their handiwork are now lost.
You can see how they did it on Inside Out screened on Monday, 25 September, 2006 at 1930 BST on BBC One in the East or nationwide for satellite viewers on D-Sat 951.