When an author comes right out and describes the character's personality traits, this is called direct characterization.  An example of this would be, "The girl is nice."  Although easy to understand, this type of characterization doesn't always make for the most interesting characters.  

More often, authors slowly reveal the personality of a character using Indirect characterization.  As we read, we form opinions about characters' personalities in much the same way that we form opinions about the people around us in the real world.  A character's personality is revealed through their words, actions, and interactions with other characters - it is shown, not told.  

 In "The Ransom of Red Chief", Red Chief's mischievous personality is given away at the very second that he is introduced as casually, "throwing rocks at a kitten on the opposite fence."  As the aspiring kidnappers approach him, he "catches Bill neatly in the eye with a piece of brick."  With just these two actions, Red Chief has already made it quite clear to the reader that he is not your average young boy.  

We also learn a lot about Red Chief's character through his interactions with other characters.  He is completely unafraid of these two strange men who have taken him away from home - rather, he is excited!  In contrast, the two men who kidnapped him are desperate to escape from him!  The final moments of the story perfectly illustrate Red Chief's effect on other characters; he's so exhausting that the kidnappers actually end up paying Red Chief's father to take him off their hands!

Describe the character types in "The Ransom of Red Chief."

Part of the delicious irony of O. Henry's story is that the character types are reversed. Normally the kidnappers would be the "bad guys" or antagonists, and the kidnapped child would be the protagonist or hero. In this story, however, Red Chief is the "bad guy" even though he is only a young boy and should be easily overcome by two older men. The boy is as obnoxious, cruel, and dangerous as any outlaw. The kidnappers, Bill and Sam, on the other hand, are eminently likable. Bill is the side-kick who carries out the orders of the "boss." The fact that Bill keeps trying to humor the boy and "play" with him even after he gets injured several times makes readers feel sympathetic toward Bill. Sam is the "mastermind" criminal, but is also, along with Bill, the protagonist. Sam uses his head, trying to pull off a crime, but he bears so little animosity toward anyone and shows so much forbearance toward Red Chief that readers like him, too. Ebenezer Dorset, Johnny's father, who should be a protagonist, is another antagonist in this story. He is also the quintessential skinflint; he is aptly named, reminding readers of Ebenezer Scrooge. Although Sam is supposed to be the mastermind, Ebenezer outwits Sam easily, and the law-abiding citizen becomes the extortionist in this humorous and ironic tale.