S1·E24 Weekend at the Beach

Two alien teenagers (technically one alien with two heads but the heads act like brothers) crash land in the desert while looking for a beach. Their arrival is detected by a hawkish General (Earth for Earthlings only!) who dispatches two crazed astronomers to gun down the aliens. Meanwhile, Penny is enjoying a weekend at the beach and Colonel Nozzaire dispatches Gadget to investigate reports of a UFO in the desert. Gadget picks up the hitchhiking aliens, but doesn't realize anything's unusual about them and takes them to the beach with the astronomers in hot pursuit.