This story is the winner of the 5th Fredic Brown award.

The alien materialised itself before them, rolled up in a cloud of golden dust and electrical discharges; then the whirlwind died away, leaving space to the strangest and most repugnant thing which has ever been seen. Dozens of slimy tentacles, greenish and constantly in motion, stretched themselves out in a shapeless knotted mass of yellow mucus, while hundreds of little eyes stared in disgusting peduncles where exploring every millimetre of the surrounding space. As long as it stayed motionless the three children watched it, astonished at it's appearance. For one infinite moment everything was still. Then, in a voice which was croaking but decided, the alien spoke.
"Listen, Earthlings!" he said, and paused.
"Wow!" exclaimed Tommy, who was ten years old, "a real monster from outer space!"
"No way!" answered eight-year-old Miki, with contempt."With all those tentacles? It's definitely a Venusian."
Mary, the youngest, continued to stare at the monster without saying a word.
"Listen, Earthlings!" the alien repeated gratingly, betraying a little impatience. But the two boys paid no attention.
"I tell you it's from outer space!" Tommy stated irritably. "I recognise it, I've seen a drawing in a magazine!"
"Rubbish," was the incredulous answer, "as if you could even tell a toad from a hen!"
"Hey, look," the alien intervened again, and this time it's tone of voice was definitely hollower. The children went dumb. "I'm talking to you, miserable little bipeds!" continued the creature in it's contemptuous tone of voice, "I bring you a message from the powerful race of the Ghor, who have gloriously conquered most of the galaxy and even now prepare to seize your insignificant little planet as well! You have no way to escape, you must surrender if you want to save yourself from the..."
"What's a galaxy?" Mary interrupted him in her sharp voice. Meanwhile Tommy went to see the alien more closely.
"Wh-what?" the alien stammered, breaking off it's pompous oratory.
"Hey, Miki, come and look!" shouted Tommy excitedly to his brother "back here it's got a kind of tail!"
"Wow, really?" the boy answered interestedly, turning to approach it.
"Stay where you are, terrestrials, or I'll atomise you!" exclaimed the alien in a shrill voice, shifting awkwardly backwards.
"Well! I want to know what a galaxy is!" insisted Mary, whimpering.
Meanwhile the two brothers, careless of the threats, kept on prodding with a stick at the poor extraterrestrial's visible appendix.
"How dare you?" exploded the poor creature indignantly, not managing to hide it's rising panic. "Stop it, I tell you!" And in a cloud of smoke and dust, it disappeared the same way it had come.
"Mary! Miki! Tommy!"
It was the calling of their angry mother!
"But where in the devil's name were you going to? I've had enough of your disobedience! I'm telling you, this is the last time I take you to Disneyland!"