Ignatius J. Reilly
Ignatius is a 30-year-old man who has spent most of his adult life earning advanced degrees and writing paragraphs on ruled notebooks in his childhood bedroom. He is selfish, unprincipled, hypocritical, gluttonous, manipulative, and deluded—an unsavory character overall. As his mother points out, he causes chaos and destruction everywhere he goes. Small moments of pathos and humanity bubble to the surface through his vulgar façade, however, as when Miss Annie describes the death of his dog, Rex. Such moments lead the reader to wonder whether his gratitude toward Myrna Minkoff in the last paragraph of the novel is sincere or feigned. Either way, Ignatius is not merely a static character. He leaves New Orleans in the end ... and feels relief. For Ignatius, that is something.
Patrolman Angelo Mancuso
Patrolman Mancuso is a kind and family-oriented man who genuinely sympathizes with Mrs. Reilly's predicament at the beginning of the novel. He introduces her to his aunt, Santa Battaglia, in order to give her life some focus outside of tending to her overbearing son. His sensitivity is not appreciated on the job, however. His sergeant treats him as the butt of a joke and forces him to wear a series of ridiculous costumes in order to attract, and presumably arrest, bad characters. Instead, Mancuso is subjected to multiple assaults and accusations until, finally, he appears in the right place at the right time and arrests Lana Lee, a bona fide criminal.
Mrs. Irene Reilly
Mrs. Reilly begins the novel as a bewildered and aggrieved mother. Her life is focused on meeting her son's needs, a task to which she is resigned. The only resistance she makes is her need to drink. She purchases alcohol against her son's wishes (he prefers that all the household budget be spent on him) and hides it in the kitchen. Once she is forced to order him off to work, though, things slowly begin to change. She becomes friends with Santa Battaglia, who encourages her to think less about Ignatius and more about herself. She starts seeing elderly Claude Robichaux, and when Ignatius is no longer the center of her world, she begins to support the idea of having him committed to the Charity Hospital's mental ward.
Jones is one of two black characters—the other is Mr. Watson—in the novel. He has a fatalistic attitude toward the culture of segregation in which he lives, viewing the lack of items for sale at the black stores and the mercenary exploitation of Lana Lee with equanimity. He simply mocks the irrational stupidity of racism. Then Mr. Watson explains to him how it is possible to bring about change (or at least make white people suffer) through sabotage. His small acts of sabotage culminate in inviting Ignatius, whom he knows Lana Lee cannot stand, to Darlene's opening night. When the cockatoo lands on Ignatius's head, and Mancuso arrives on the scene, his coup has exceeded expectations. Indeed, the Levys decide to reward Jones for pulling Ignatius out of the way of the bus by giving him an award and a better job.
Lana Lee is an unrepentant capitalist. Ignatius calls her the "Nazi proprietress." She makes sure the drinks in her bar are routinely watered down and the school children to whom she sells pornography get exactly what they want (pictures of teachers). She knows exactly how to profit the most from every situation. Streetwise, she also knows how to spot a cop, so her pornography ring has flourished without notice. Unfortunately for Lana, Mancuso is not much of a cop, so when he steps into the fracas on Darlene's opening night, dressed like a gangster or flashy businessman, she fails to see through his disguise and shows him the pornography picture of herself, leading to her arrest.
Mr. Gus Levy
Mr. Levy is haunted by the success of his industrialist father, Leon Levy, the man who built Levy Pants into a success. In fact, his wife, Mrs. Levy, cannot let Mr. Levy forget about his father's success. She constantly nags him to be more like his father, if not for her sake, then for that of her daughters. Mr. Levy himself gets depressed whenever he enters the factory, and he spends his days avoiding it. The threat of a $500,000 lawsuit proves to be the catalyst he needs to take responsibility for his life. He stands up to his wife, announcing that he will make Bermuda shorts from now on. Secretly, he ruminates that Mrs. Levy will be out of the picture.
Myrna Minkoff—the "minx" as Ignatius calls her—is the sole character in the novel from outside New Orleans. She attended Tulane University with Ignatius, where the two presented a united front against their common enemy, history professor Dr. Talc. After returning to New York, she has moved from one progressive social reform project to the next. She subjects Ignatius to various written personality analyses, encouraging him to leave the womb and join her in New York. Eventually, she comes down to get him.