presents an interesting dilemma for physicists. It would be seem clear that he is not transparent (thus allowing light to pass through him and casting no shadow) because he is visible to the human eye (and would thus seem to be reflecting light back to a viewer's eye). And yet, all evidence would suggest that no shadow follows him.
MIT scientists finally solved this controversial and puzzling issue in 1997 with the discovery that he is in fact largely transparent but, like the star he is, Manny actually produces his own light from with by a process similar (though not identical) to solar fusion. Although the actual mechanism remains theoretical (and could provide the basis for a new unified field theory), normal light passes through Manny with perfect efficiency, thereby eliminating shadows. Our ability to see Manny is therefore not due to reflected light, but rather is a projection of his innate luminosity.
Strangely, Manny's transparency does not extend throughout the entire electromagnetic spectrum, as advanced imaging equipment has shown that he actually absorbs gamma and cosmic rays. This results in a very peculiar shadow, albeit one that cannot be seen by humans. Which only raises more questions, particularly who the audience for the extremely exclusive shadow-puppet soirees Manny has been often accused of hosting within his ominous skull-shaped castle deep within rural Oregon, the so-called Hacienda del DOOOOOOM.