The Pleiadians through Barbara Marciniak say
"The circles and shapes being put on earth are here to assist you in holding and managing your frequency and having the courage to live your light. They make frequency information available in a very subtle way, and no one can figure them out yet. These shapes are all connected to one another, and if they were all written out simultaneously on some farmer's field, something would happen to them immediately. They are spaced from one continent to another, and they move a frequency band around the planet that will help activate earth's grid-work. They will allow you not to feel so weird with what you know and to feel more comfortable with the changes in frequency as they occur.
"This is just a little bit of what the crop circles do. They are quite interesting. Many of them are designed and constructed by what some call 'Ascended Masters'. There is also a joke behind them. You must understand that some beings, as they become very evolved, develop a tremendous sense of humor. They see the humor in all things.