Trainee Clippers are called Colts. Each Colt is selected and mentored by a senior Clipper, who oversees their training. They are trained from childhood, often bought as slaves and separated from their families. However, many boys and girls are eager to join, every child gets a chance to become a Clipper, and it is much preferred over a life in the poppy fields. In "White Stork Spreads Wings", Waldo sates that they are called Colts because "we gotta break 'em, like wild horses. That's the only way to make a Clipper out of a boy."