Check out the latest crop circle:
What is amazing about this one is that the number pi is encoded in it. Start in the center and note the length of each segment. The first one is 30% of a full circle, so 3. Then there is a decimal point. The next is 10% of a full circle, so 3.1. Then we have 40% of a full circle, 3.14, and so on. It goes to nine decimal places.
In considering how this thing got in that field, as I was figuring out how pi is encoded I noticed something. Why make 30% of a circle represent the number 3? This means that 100% represents 10. Now you must know that there is nothing special about ten. We happen to have ten fingers and ten toes. But there is no particular reason for when you turn ten years old that it must be "double digits." Look at nine apples, then look at ten apples. Why should nine apples require one digit, and ten require two? There is no intrinsic natural reason, except maybe it is easier to count on our fingers.
What I am talking about is number systems. Probably the next best known number system to decimal is binary. In binary, two is double digits. Remember this? "There are 10 kinds of people: those who know binary, and those who don't." (If you aren't catching on, "10" in binary is two.) Why not encode pi in a crop circle in binary? You can see the string of zeroes and ones for pi at http://www.befria.nu/elias/pi/binpi.html, for example.
So the whole thing is fishy. There is no natural explanation for pi to be encoded in this crop circle, especially in the formalism of decimal numbers.
Conclusion: the aliens that made it have ten fingers.