The Gendarme and the Creatures from Outer Space

Ludovic Cruchot (Louis de Funès), the bungling inspector of St. Tropez, discovers that humanoid aliens are walking among the town's residents and drinking oil. Jean Girault gives him one test to work with: tap a suspect, and if the body rings like an empty garbage can, it isn't human. Cruchot has to make that case to his superior Gerber (Michel Galabru), and he flaps and shouts at everyone who won't listen.