A newspaper film critic, Billie is a single woman who finds herself "accidentally" pregnant after a one-night stand with a much younger guy, and decides to keep the baby... and the guy.
After breaking up with her commitment-phobic boyfriend, Billie has a fling with a younger guy, ends up pregnant and decides to keep the baby – and the daddy.
While snooping through Zack's belongings Billie discovers a note addressed to her, that he never finished writing and sets out to find what Zack is hiding.
Billie's pregnancy makes her more attractive to members of the opposite sex, including Zack, who is turned on by her new curves. However, an unfortunate incident with self tanning lotion, forces Zack to reject Billie's advances toward him.
Billie and Zack discuss their feelings on dating and agree to see other people, however, Billie's pregnancy gets in the way of any potential love connections.
Billie tries to live vicariously through Zack and Davis by offering up dating advice to them. However, things take a turn, when the objects of the boys' affection reveal their true intentions.
Billie and Zack have their first big argument after Zack tries to surprise Billie by installing a low flow toilet.
Billie unintentionally causes Abby and Nick to break up when she asks them to be Godparents. However, after a fun night on the town with Davis goes too far, Billie must stop Abby before she does something she will regret.
When Billie starts dating a colleague from her newspaper, Zack is unable to hide his jealousy.
Billie is threatened when James hires another film critic at the paper and sets out to prove how valuable she is.
When Billie and Zack take instructional parenting classes separately due to their schedules, Billie goes with Olivia and Abby. However, the course quickly becomes a competition when Abby outshines Billie at all the tasks.
Worried that she'll ruin Christmas – as she has in previous years – Billie tries to hide from her parents the fact that Zack is living with her. Meanwhile, Abby's husband, Nick, tries to impress their father.
Abby and Nick have their respective significant others spend time with Billie and Zack to prevent them from finding out about the surprise shower they are planning. However, their plan backfires when both Billie and Zack dislike their new buddies.
While working on a story with Sully, Billie gets some surprising news about the newspaper. Meanwhile, Zack and Davis go into the sandwich business together.
Not wanting to sound like a nag, Billie manipulates Zack into doing chores around the apartment; however, her plan backfires when Zack takes the initiative to "decorate" the nursery. Meanwhile, to earn extra cash, Davis gets a job at a gay bar.
Billie invites herself to Zack's high school reunion but worries that she can't compete with his hot, ex-girlfriend in her pregnant state. Meanwhile, Olivia helps Abby host a party where they try to sell Abby's miracle youth juice.
Zack is upset when Billie hires a baby nurse without consulting him. Meanwhile, Davis and Ryan are faced with a difficult choice when they learn surprising news about the nurse.
Billie pretends to go into labor to save Zack from getting a traffic ticket after they're pulled over for speeding. Meanwhile, Olivia and Davis go shopping for a baby gift.
After faking labor pains to get Zack out of a speeding ticket, Billie goes into labor - for real. Unfortunately, things take a turn when Zack gets busted by the officer they had initially lied to and is hauled off to the police station.
