Le Gendarme et les extra-terrestres (1979)

The actions once again take place in the small French town of Saint-Tropez. This time, Chief Marshal Cruchot has discovered that aliens have arrived in their town. The aliens—which are made of iron—can duplicate the forms of humans and are skilled in the ways of telekinesis; they promptly impersonate the policemen. Cruchot finds that the only two ways to tell them apart are the fact that they drink oil and that, when struck, they make a sound similar to that of an empty rubbish bin. Hilarity, of course, ensues, especially when identities get mixed up: Cruchot is assumed to be mad.