A few simple folds will lead to hours of fun.
Using a square (not rectangular) piece of paper, position it so the paper looks like a diamond. Fold the far left corner to the far right corner to create a crease.
2. Unfold it and then fold the square in half.
3. Unfold it again, and then fold all of the corners of the square into the center.
4. Flip it over and fold the corners in again to make a smaller square.
7. Work your fingers into the open flaps and push the top corners out to form a 3-D shape.