We present a novel method for creating asymmetrical particles with unusual, flattened shapes from colloidal latex microspheres pinned at an oil-water interface. The shape and degree of asymmetry are controlled by incubating particles for minutes to tens of minutes at an elevated temperature. Estimates of the surface energy and work account for the shape-change mechanism in which heated particles deform as they spread at the oil-water interface to minimize the contact between these immiscible phases.