Alfie is an unassuming man who possesses the inherited magical ability to repeat any moment in his life by thinking the word "twice." He records his altered timelines meticulously in a black marble composition notebook. Having spent part of his childhood in Kenya before moving back to the United States after his mother's sudden passing, he struggles with anxiety and a desire to control reality. He begins using his extraordinary gift as a child to fix poor test grades, erase embarrassing social encounters, intervene in school bullying, and survive deliberately dangerous stunts, constantly weighing his personal desires against the ethical boundaries his mother set for him.

Gianna is an aspiring photographer whom Alfie originally meets as a young girl in Kenya, where she goes by the nickname "Princess." She possesses a strong sense of morality and a highly grounded perspective on life. Unaware of Alfie's supernatural abilities, she believes in accepting the past rather than trying to change it. Alfie reconnects with her years later at a zoo in Miami, where she recognizes him by a shared memory of an elephant, prompting him to follow her to Boston University.

Vincent is a practical detective stationed in the Bahamas who investigates casino fraud. He refuses to believe that anyone can guess three roulette numbers by chance, leading him to press Alfie for a logical explanation. Constantly chewing Life Savers as a substitute for smoking, his strictly rational worldview is challenged by the fantastical claims within Alfie's composition notebook. He is determined to uncover the real source of the money and the identity of the woman to whom Alfie wired his winnings.

Alfie's mother dedicates her time to missionary work in a rural Kenyan village. Before succumbing to a fatal bug bite, she passes down the family's secret ability to her young son. She serves as Alfie's primary ethical guide, explicitly warning him never to use his temporal powers for greed and explaining that the gift cannot permanently reverse death. Her memory deeply influences Alfie, driving him to honor her by playing the piano she left behind.

Following his wife's sudden passing, Alfie's father uproots his life in Kenya and moves his son back to the United States. He is a grieving widower who struggles to connect emotionally with Alfie, leaving the boy to process his trauma largely on his own. His subsequent attempts to rebuild his life, including entering the dating scene and bringing new women into their home, cause frequent friction and misunderstandings with his son.

Known affectionately as Yaya Nina, she is the matriarch of the family who lives in Florida. She shares the genetic ability to rewind time, having used it during her own youth. Having lived through the consequences of altering her own romantic history, she understands the heavy burden of the gift. She attempts to pass her hard-earned wisdom down to Alfie, warning him specifically against using his power to force romantic perfection.

Wesley is an ambitious, high-achieving student and Alfie's closest friend during his adolescence. He frequently excels in his endeavors and plans to join the Marines, fully confident in his future safety since the Vietnam War has ended. He provides a sounding board for Alfie's teenage anxieties and receives occasional anonymous help from Alfie's temporal powers.

Adeline is a woman who briefly marries Alfie's father during Alfie's high school years. She immediately imposes strict new rules on the household, insists on calling Alfie by his full formal name, and removes photographs of his late mother. Her abrasive behavior deeply upsets Alfie, motivating him to take drastic action.

The elephant is a gentle creature that Alfie and Gianna frequently play with during their youth in Kenya. The animal represents a time of pure innocence for Alfie before he discovers the heavy burden of his magical abilities. Its memory serves as a crucial connection point for Alfie and Gianna years later.

Mike is Gianna's college boyfriend. He forms a barrier to Alfie's romantic pursuits, demonstrating to Alfie that manipulating time cannot simply manufacture a mutual connection. He represents the natural progression of Gianna's life independent of Alfie's interference.

Jo Ann is a high school student who becomes the target of Alfie's teenage affections. When he uses his temporal powers to reinvent himself to match her specific interests, he discovers her prejudiced worldview, entirely changing his opinion of her and teaching him that some people are not worth altering reality for.

Lizzie is a high school student who genuinely likes Alfie during his natural timeline. However, when Alfie alters the past to pursue someone else, he inadvertently erases her initial affection for him, giving him early insight into the unpredictable consequences of his abilities.

She remains at home while her husband investigates casino fraud abroad. Their phone conversations reveal a strained marriage, as she openly doubts his status as a real police officer, providing a grounded contrast to the romantic themes in Alfie's notebook.