We've probably all seen a picture of a crop circle here and there. They've been occurring since the 1970s and for awhile, people thought they came from aliens.
Now we know of course that they're simply a hoax, created from pranksters who obviously have no inkling of the energy and time it takes to grow crops, or any respect for the fact these crops are FOOD that nourishes PEOPLE. Anyway, elaborate crop circles require some precision to make.
There are various pranksters who've claimed responsibility for crop circles, and the prevalence of these circles has increased with the spread of the Internet.
This is presumably because people see photos of crop circles in other countries and attempt to replicate or outdo them.