Ambiguous Cylinder "Full Moon and Star"
This is a short cylinder, but the appearance changes drastically when it is reflected in a mirror. The direct view appears to be a full moon whereas the mirror image appears to be a star. The edge of the cylinder is a space curve and hence the appearance can change when we change the viewpoint. However, this object is made in such a way that the length of the cylinder is homogeneous, and hence our brains interpret the edge as a planar curve generated by cutting the cylinder with a plane perpendicular to the axis of the cylinder. Because of this interpretation, we have an impression of an impossible object.