Fran is self-conscious about her age; she often claims to be 29 (In one episode stating her actual age was 32, without notice), regardless of how much time passes. Fran's long and mostly fruitless search to find a husband was sparked by her mother's inexorable pressure for Fran to be a wife and mother. This is a consistent plot device throughout the first four seasons, leading to many humorous and compromising situations.
She is not a traditional nanny, so when raising the kids, she gives them street smarts and life tricks. These tactics have a healthy and positive effect on the children. The youngest, Grace, eventually graduates from therapy because of Fran's warm and involved approach. It is worth noting that Fran's lower class knowledge and influence does more for the children than the upper class, structured rearing they were limited to before she entered their lives. She is loving, caring and mildly snarky toward her adversaries.
Despite her weariness and exasperation over her mother's constant disregard for boundaries and persistent interferences in other people's lives (especially Fran's life), Fran seems to have inherited this personality trait from her mother. Fran often meddles (albeit with benevolent intentions) in other people's problems and oversteps boundaries to do what she believes is best for the people she cares about.
The romantic tension between Maxwell and Fran lasts until the couple gets engaged in the fifth season; following several snafus, they are finally married in the season 5 finale. Until that point, they always address each other with proper employer-employee politeness, i.e. "Miss Fine" and "Mr. Sheffield.
Maxwell finally confesses to Fran that he loves her (for the first time) when their plane to New York from Paris meets some turbulence, and he believes they may crash. So ends season 3 on a cliffhanger as to what will eventually happen between them.
Upon returning home, at the beginning of season 4, Maxwell immediately revokes the statement (this is later referred to as "the thing" and is held over Mr. Sheffield's head with glee by Fran).
However, by the fifth season, Maxwell and Fran begin a tentative romantic relationship, which consisted of a very large milestone: calling each other by their first names. Maxwell proposes marriage (a move that sends C.C who had an obsessive crush on Maxwell and jealous hatred of Fran, to a mental hospital). Later, they are married, after C.C. gets back in town. C.C. even tries to walk down the aisle with Maxwell to try to marry her. Later Fran legally adopts Maggie, Brighton, and Gracie.
Fran finally gets pregnant in the season 5 episode Oh, Say, Can You Ski? after a long battle of trying to get into that state. Soon after, it is revealed that they are having twins. In The Finale: Part 1, Fran goes into labor. It ends with her, and the rest of the gang going to the hospital so Fran can give birth. When Maggie, Brighton and Gracie ask their father who he thinks the twins are going to look like. Maxwell replies that it doesn't matter who they look like, as long as they're, "...happy, and healthy, and...sound like me".
They finally give birth to fraternal twins, Eve and Jonah. Jonah, who was born first, was named for Fran's side of the family, but was more reserved like his father; and Eve, who was born a few minutes later, was named for her father's side of the family, but was more nasally and boisterous like her mother.
Despite the fact they stopped using each other's last names to address each other when they married, Fran and Max would still switch to their boss/employee roles out of habit. When Maxwell is angry with her, he will instinctively shout "Miss Fine!", causing a worried Fran to reply, "Oh no, I'm Miss Fine again!". The same is true for Fran, who calls Maxwell "Mr. Sheffield" in bed. Before they got married, Fran had many fantasies of them making out or close to being in bed together.
- Fran reveals her age is 30 in "Take back your mink", which makes it ironic in a late episode Fran's age couldn't be verified by the FBI.
- In the finale, she gives birth to boy-girl fraternal twins.
- She likes C.C. even though C.C. hates her.
- She appears to be an emotional eater.
- Her favorite store throughout most of the series is Loehmann's.
- She dislikes coral lipstick.
- Her preferred brand of hair dye is Lady Clairol.
- She doesn't like to waste food.
- She owns several bathrobes.
- She seems to favor animal print clothing.
- She is an expert on television culture and has the TV Guide memorized.
- She adores meeting celebrities and often sees through Maxwell's attempts to trick her into leaving the house when a celebrity visits the Sheffield residence.