The alien repeated the greeting. There was no response. The alien, annoyed by what he perceived to be the gas pump's haughty attitude, drew his ray gun, and said impatiently, "Greetings, Earthling. We come in peace. How dare you ignore us in this way! Take us to your leader or I will fire!"
The other alien shouted to his comrade "No, you mustn't anger him...!", but before he finished his warning, the first alien fired. There was a huge explosion that blew both of them 200 meters into the desert, where they landed in a heap.
When they finally regained consciousness, the one who fired turned to the other one and said, "What a ferocious creature. It nearly killed us! But how did you know it was so dangerous?"
The other alien answered, "If there's one thing I've learned during my travels through the galaxy, it's that if a guy has a penis he can wrap around himself twice and then stick into his own ear, don't screw with him!"