Now let's analyse the characters of the story. There are five of them:

Sue - a young artist, Johnsy - a young artist, Behrman - an old artist, a doctor. Mr. Pneumonia.

 The main characters are Sue, Johnsy,  and Mr. Behrman . The secondary character is a doctor. Sue, Johnsy and  Mr. Behrman are protagonists and Mr. Pneumonia - antagonist.

Sue is shown as a young girl who is ill.She think that she will die. She is shown very kind and good person. Here the author uses indirect characterization of the character, he shows only their deeds. For example, Sue always takes care about Johnsy. The author is sympathetic towards her.  Mr.Bergman is depicted inderectly: through his appearance, lifestyle and deads : "Old Behrman was a painter who lived on the ground floor beneath them. He was past sixty and had a Michael Angelo's Moses beard curling down from the head of a satyr along with the body of an imp. Behrman was a failure in art. Forty years he had wielded the brush without getting near enough to touch the hem of his Mistress's robe. He had been always about to paint a masterpiece, but had never yet begun it. For several years he had painted nothing except now and then a daub in the line of commerce or advertising. He earned a little by serving as a model to those young artists in the colony who could not pay the price of a professional. He drank gin to excess, and still talked of his coming masterpiece. For the rest he was a fierce little old man, who scoffed terribly at softness in any one, and who regarded himself as especial mastiff-in-waiting to protect the two young artists in the studio above."

    With the help of the narrative description of what Mr. Pheumonia is doing, we can guess the author’s attitude towards him. O.Henry personified this disease in this short story. For example: «a cold, unseen stranger, whom the doctors called Pneumonia, stalked about the colony, touching one here and there with his icy fingers. Over on the east side this ravager strode boldly, smiting his victims by scores, but his feet trod slowly through the maze of the narrow and moss-grown "places." Mr. Pneumonia was not what you would call a chivalric old gentleman. A mite of a little woman with blood thinned by California zephyrs was hardly fair game for the red-fisted, short-breathed old duffer»