Elsie is a recently graduated theoretical physicist working as an underpaid adjunct professor at three different Boston universities. To cover her living expenses and medical supplies for her Type 1 diabetes, she moonlights as a fake girlfriend on the Faux app. She possesses a well-honed ability to read people and alter her personality to fit their expectations, a survival mechanism born from childhood insecurities.

Jack is an experimental physicist and the head of the Physics Institute at MIT, where he publishes under the name Jonathan Smith-Turner. He harbors a deep disdain for dishonesty and immediately suspects Elsie is deceiving his family when they meet. Years ago, he wrote a highly controversial hoax article that discredited theoretical physics, creating a lasting rift between him and academics like Elsie.

Christophe is a French theoretical physics professor at Northeastern University and the former editor of a prestigious academic journal. His career suffered a major blow following the publication of a hoax article by Jonathan Smith-Turner. He acts as the sole gatekeeper for Elsie's early career, demanding strict loyalty and gratitude for his mentorship.

Georgina is a highly capable and confident experimental physicist. She frequently collaborates with Jack Smith and is the preferred candidate for the newly created position at MIT. Unlike Elsie, she is self-assured and straightforward about her professional goals in a male-dominated field.

Greg is a client on the Faux app who hires Elsie to pretend to be his girlfriend. He uses the service to appease his wealthy, demanding mother who constantly pushes him to settle down. He genuinely likes Elsie and considers her a friend, complicating her professional boundaries.

Cece is a linguistics PhD candidate, cinephile, and Elsie's roommate. Like Elsie, she works for the Faux app to make ends meet. She frequently benefits from her roommate's inability to say no, asking for small favors while remaining largely unaware of the toll it takes.

Monica is a member of the MIT physics department who actively advocates for Elsie's application. She is deeply invested in the long-standing feud between theoretical and experimental physicists, pushing Elsie forward despite the hiring committee's preference for an experimentalist.

Millicent is Jack and Greg's sharp-witted grandmother. She frequently feigns emergencies to force Jack to visit her and pays close attention to the dynamics between her grandsons and the people they bring home.

Caroline is Greg's wealthy, overbearing mother and Jack's stepmother. She is fixated on the idea of her son finding a partner, creating the pressure that drives him to use the Faux app.

Austin is Monica's son and a former client of Elsie's on the Faux app. His previous encounter with Elsie was disastrous, leading to a highly uncomfortable reunion during her academic interview process.

Grethe was a theoretical physicist and Jack's biological mother who died when he was an infant. Her academic career and the treatment she received from her colleagues heavily influence her son's actions years later.

Kirk is a wealthy scientist and entrepreneur who uses the Faux app to hire Cece. Their arrangement gradually shifts toward a more consistent, long-term agreement.

Olive is a biologist and a close friend of Jack. She represents a positive example of a woman navigating the challenges of STEM and quickly forms a friendly connection with Elsie.

Adam is one of Jack's closest friends, functioning as part of his chosen family outside of the biological Smith relatives.

Lucas is one of Elsie's twin brothers. He is frequently embroiled in dramatic personal disputes, requiring his sister to act as a peacekeeper to maintain family harmony.

Lance is Elsie's other twin brother, constantly arguing with Lucas over shared romantic interests and forcing their sister into the middle of their chaos.

Elsie's mother is highly dismissive of her daughter's career ambitions and personal struggles. She expects Elsie to manage the family's emotional burdens while showing little interest in the difference between an adjunct and a tenure-track professor.