His and Sheldon's mom says that she was tired of hatching eggs and needed a vacation. (May 6,1986) Booker and Sheldon were still eggs when Orson found them abandoned and decided to hatch them. Nobody in the barnyard knows what happened to their parents.
Booker is extremely adventurous, outspoken, and he's sensitive about his height. He often chases worms, but can never seem to catch them, which aggravates him to no end. Though he does occasionally get even with the worms in the comics.
In the comic, he often called Orson "Mom", but in the cartoon, when it's discovered how Booker and his brother were hatched, he calls him "Mommy".