Isaac Asimov 
Youth [PDF ebook] 

When strange animals land in Red’s yard, he and his friend Slim agree to keep it to themselves. The creatures are unlike any that they’ve ever seen before, and are — to them — animals that would make a fortune putting on a show at the circus. All the while, their fathers are fretting over the arrival of interstellar diplomats, on whose trade their civilisation may have to rely on to survive. Despite the urgency of the mission, however, neither hide nor hair of them have been seen…