This is one of my favorite drawing tutorials on the site. It introduces you to a very interesting principle -- making drawings out of recognizable, simple shapes. While you can draw all sorts of creatures and other things from a pear shape, which is so well outlined below, that's just the beginning.
You can draw almost anything if you break it down into simple shapes. Shapes like circles and ovals and triangles have been used for decades by artists to "block out" their drawings. Even sketching makes use of these "building blocks"; if you look very carefully at the first, lightest lines, a lot of sketch artists will draw shapes first, then use those basic forms to guide the fast, more flowing lines they use to make up the bulk of their drawing.
One of the best uses of this principle is using alphabet shapes to draw things. This is especially good for young children who are learning the alphabet anyway. And because children can be so incredibly creative, it can be a real treat for a teacher or a parent (or both) to give an assignment of drawing a few things from alphabets and seeing what they get back as completed drawings. These are ideal works to hang on the wall, because that way other children can see how far they can go just by learning their letters. Can you imagine how an "A" would become a house, or how a "Y" could become part of a cat's face?