BIG DOG by Lois G. Grambling. Grandma Annii's Story Time

Willie gets what he thinks is a "big dog" from the Pedigree Dogs ONLY pet store, but it's really a dinosaur. Others see the truth, but the child assures them that it is a dog, until his pet lays an egg, and Willie accepts the truth. His last thought is that he hopes a "BIG DUMB CHICKEN doesn't hatch out of that EGG!"