trust me, a well thrown egg will chip the clearcoat and probably a layer of paint (maybe down to the primer if throwing hard enough) in a spiderweb looking fashion. to boot, it is impossible to touch up because of the way the chips occur. even if you wash the car off, the chips will remain, so any egg thrown WILL result in damage to your vehicle. to remove these spiderweb blotches you will need to repaint the entire panel, unless you are just a wizard with spot repair
i wouldn't even recommend anyone attempt throwing an egg at a car to see if the spiderwebb chips occurs... just take my word that it will:
now if a car was egged good, imagine that, some probably worse, everywhere