Marcus is an earnest and literal-minded twelve-year-old boy who recently relocated from Cambridge to London. Raised by a highly opinionated mother, he holds unconventional views and habits, including strict vegetarianism and a preference for older music. His lack of understanding regarding social norms severely isolates him from his peers. He assumes a heavy burden of responsibility for his mother's well-being and actively searches for ways to fix her depression.

Will is a thirty-six-year-old bachelor who lives comfortably off the royalties of a popular Christmas song written by his father. He actively avoids adult responsibilities and long-term commitments, preferring a life filled with daytime television and casual dates. He maintains a facade of trendy indifference and frequently invents elaborate stories to attract single mothers.

Fiona is a music therapist and Marcus's mother. She holds strict ethical principles, enforcing vegetarianism and a rejection of popular culture on her household. Despite her strong ideological convictions, she struggles with severe depression that prevents her from effectively parenting Marcus or recognizing his daily difficulties at school.

Suzie is a beautiful single mother whose husband abandoned her during her pregnancy. She attends a local single parents support group, where she catches Will's attention. She serves as a close confidante to Fiona and regularly steps in to look after Marcus during crises.

Rachel is a glamorous, bohemian children's book illustrator. As a single mother to her son Ali, she leads an engaging life that immediately attracts Will. She values authenticity and emotional investment, naturally challenging the men she dates to step up to her level of maturity.

Ellie is a rebellious fifteen-year-old student known for constantly getting into trouble. She wears dark lipstick and clothing featuring the band Nirvana. She harbors a deep anger at the world and idolizes Kurt Cobain, finding comfort in the singer's darker themes.

Clive is Marcus's father and Fiona's ex-husband. He works in social services but remains largely absent from Marcus's daily life. He lives in Cambridge with his girlfriend and remains completely disconnected from the immediate struggles his son faces in London.

Angie is an attractive single mother of two young children. Her physical resemblance to Julie Christie draws Will's interest, leading him to pretend he enjoys playing a stepfather role. She carries significant emotional baggage from her previous relationship.

Ali is Rachel's twelve-year-old son. Growing up with an absent father and witnessing his mother's past unsuccessful relationships, he acts highly territorial and insecure regarding new men entering Rachel's life.

Megan is Suzie's young daughter. Her father abandoned the family before her birth, leaving her to be raised entirely by her mother within the network of the local single parents group.

Lee Hartley is a school bully who targets students he perceives as weak or different. He leads a gang of similarly aggressive youths who take pleasure in tormenting Marcus over his strange clothing and habits.

Nicky is a computer-loving student at Marcus's school. He and his friend Mark are social misfits who initially share space with Marcus before realizing the new student draws too much negative attention from the local bullies.

Mark is a quiet, computer-enthusiast student who attempts to keep a low profile. He actively distances himself from Marcus to avoid the severe harassment that follows the boy around the schoolyards.

Lindsey is Clive's girlfriend, living with him in Cambridge. She represents the new life Marcus's father has built away from London.

John is one of Will's few friends. He leads a conventional life with a job and a growing family, standing in direct contrast to Will's fiercely guarded bachelorhood.

Christine is married to John. She frequently expresses exasperation at Will's refusal to engage with adult milestones like marriage or child-rearing.

Imogen is John and Christine's newborn daughter. Her birth prompts her parents to ask Will to step up as a godfather, a request that highlights his aversion to commitment.

Simon is Angie's ex-partner and the father of her children. His past behavior, which included infidelities and a work addiction, sets a low bar that Will initially enjoys clearing simply by being present.

Joe is Angie's youngest son. His open appreciation for Will's attention briefly makes Will feel validated in his temporary role as a father figure.

Katrina is Ellie's mother. She is friends with Suzie and struggles to manage her daughter's increasingly rebellious behavior following her own divorce.

Ms. Maguire is a young and nervous English teacher at Marcus's school. She struggles to maintain classroom authority and attempts to secure favor with the majority of her students by ignoring their poor treatment of social outcasts.