An oversharpened image tends to have what we call jaggies along all or some of the edges. Take an image and if you have Photoshop or some other program, hitImage + Sharpen two or three times. Then look at the edge of the body or the cheat lines on the plane. They should be straight, but now they probably have little steps along the edge. JAGGIES.
Some people are like Slinkies. They bring a smile to your face when you push them down a flight of stairs.