Sir Basil was one of Charley Chicken’s early ancestors. Basil was an adventurer and discoverer, who led an exciting, though brief life. Being born, or rather, hatched with big brains, he is famous for many famous innovations and finding new ways for Fowlkind to do old things. Sir Basil was the first and last son of the Great Original Rooster, and the whole Charley Chicken family is descended from him.
All this was before the family married into the d'Ostriches and the Emus. So Sir Basil was not a fully-developed Tall Fowl like Charley Chicken.
Sir Basil's body may not have been that of a fully developed Tall Fowl but that really didn't matter. When you have super brains, you can make do with an ordinary body. For instance, Sir Basil had invented the Chickenshute. This device allowed Chickens to float great distances. Sir Basil had looked at the way common chickens used to flap to escape attacks. He would always wonder why common chickens would always say they couldn't fly, but when they really had to, they could get over great obstacles. If only they would learn how to keep quiet whilst escaping, they could evade many attackers
Sir Basil always kept written notes of his thoughts and ideas, because he knew that his ideas were Truly Great Ideas that came to him from the Floating Feathers of the Great Chicken. Wisely, Sir Basil knew that he could not remember everything (even though he was a Great Fowl and not a common chicken, he still didn't have the perfect memory that Great Original Rooster wished for). So the Cleverest Chicken of the Brood wrote down a lot of his dreams, thoughts and ideas, so that he could see, many years later, if he was really still being clever.