The fourth season of The New Adventures of Old Christine finds Christine still enduring encounters with the "meanie" moms at her son's posh private school and dealing as her charming ex- husband, Richard.
After her divorce from Pete is finalized, Barb learns her immigration status is in jeopardy and she may have to return to her homeland, the Bahamas, until she gets her paperwork straightened out. In order to solve Barb's immigration problem, Christine decides she and Barb should get married to keep Barb in the country. In the meantime, Richard has decided that he's ready to marry New Christine, but she refuses until he comes up with a proposal that's creative.
Christine realizes she is in a really great place regarding Richard and New Christine's engagement, until Richard asks for his mother’s engagement ring back. Christine refuses, until Richard offers to buy her a new ring. While they're shopping, Christine picks out a ring that Richard says New Christine would love. When Christine realizes that the only reason Richard is giving New Christine the old ring is to please his mother, she tries to talk some sense into him.
Matthew has his first client, a very attractive young woman whose problem is that she wants to kiss anyone who seems to have a lot of knowledge. This ends up including Matthew.
Barb is profiled in a local black business owner’s magazine, and it brings a ton of new business to the gym, most of which are black women. All of a sudden, Christine doesn't feel so comfortable in her own gym. She wonders if Barb understands what it's like to feel different from everyone else, leading Christine to realize that maybe she's a little bit racist after all. Because things are so busy at the gym, Christine has Richard and Matthew look after Ritchie. She gives them lots of instructions, but they’re dismissive and end up losing Ritchie.
Christine has been burning the candle at both ends -- working hard and trying to be a good mom. Ritchie decides he wants to join the reptile club at school and tells Christine all she needs to do is get the permission slip in on time. When Christine realizes that she's forgotten yet again, she asks the Reptile Guy (Jeffrey Tambor) to make an exception. He says the only way he'll consider is if Christine will go on a date with him. As creepy as he is, Christine is determined not to let Ritchie down, and so she complies.
Christine is distraught when Ritchie stops saying "I love you" to her. When she reveals her distress to Matthew, she also admits that she's been sleeping in Ritchie's room every night. Matthew tells her that if she's not careful, Ritchie will end up like him -- he can't go to sleep without talking to their mother. They spend the night helping each other break these habits.
Barb and Christine meet two cute guys in the video store and end up going on a double date with them. Barb is concerned with how quickly Christine seems to get attached and coaches her on how to be cool and just have fun for the night. But when Barb gets a call from her date to go out again and Barb reveals that she thinks he might be the one, Christine feels cheated by Barb's advice. Richard drags Matthew chair shopping for the wedding and panics about settling down with just one chair.
Christine and Patrick have been dating for a little while and everything seems to be going really well. Patrick has even accepted Richard's constant presence in Christine's life. Her new attitude is take it or leave it, and Patrick has decided to "take it." But when Christine invites Richard to join them on an intimate date, Patrick isn't quite as thrilled and it looks like he might leave it.
Barb tells Matthew a "secret" that he can't tell anyone because he is her psychologist.
Christine, et al, brace themselves for another disaster when they go to see Ritchie in his school play. But Ritchie shocks them all with an incredible performance and further, he's invited to audition for a national commercial. Christine wants to pursue it and Richard doesn’t, so they let Ritchie decide. Ritchie says no and Christine is disappointed. She and Matthew discuss how their lives would have been different had their mother encouraged them at their true love – dancing, which leads to a dance-handoff between them, and makes Christine decide that she knows what’s best for her kid even if he doesn't. She has Ritchie audition and Richard is livid until he finds out Ritchie actually got the commercial.
Christine and Patrick are going strong. She's convinced she's found the perfect man until he loses to her in a friendly game of tennis. While Christine knows she might not be the best winner, she is shocked by the way Patrick behaves when he loses. In order to prove to her friends that it's not the result of her rubbing her winning in Patrick's face, she plans a game night and arranges for Patrick to lose.
Matthew freaks out when people start telling him his girlfriend, Lucy, is exactly like Christine.
Everyone goes to Christine and Matthew’s parents for Thanksgiving, a trip Christine always looks forward to given her mom's proclivity for giving her a hard time about her divorce. But when they arrive, they realize something is off. Their mom is acting weird and Christine’s father is nowhere to be found. They initially suspect their mother killed him and hid the body, but then learn their parents have split and their mother was too embarrassed to admit it -- especially after giving Christine such a hard time about her situation.
Megan Mullally guest stars as the Bloom Gym franchise organization owner who comes to check in on how Christine and Barb's gym is doing. When they reveal their marriage to her, she tells them it's against the rules of the company and shuts them down. New Christine and Richard decide they don't want to have any children. Richard agrees to get a vasectomy but can't go through with it and refuses to tell New Christine.
Having been stripped of their franchise, Christine and Barb decide to turn the gym into a spa. They are overjoyed by how quickly their new business has become a success -- until they find out they're actually running a brothel.
At an orientation for Richie's new Junior High, Christine runs into an old school mate who spread rumors about her that ruined her life in 7th grade. New Christine is enamored with Barb's ability to speak her mind.
While Matthew plans a stellar bachelor party for Richard, New Christine insists she was content with her office bachelorette which consisted of a coffee break at the downstairs shop. Barb convinces Christine that they should take New Christine to Vegas for a proper bachelorette where she tries tequila (and many other things) for the first time.
Richard's brother comes in for his bachelor party and is totally insulted that Richard has asked Matthew to be his best man.
Barb has found a new condo to live in and Matthew is moving in with Lucy, leaving Christine on her own (Ritchie is going away to camp for a week) for the first time. Christine feels abandoned but puts on a brave face; unfortunately, she locks herself out and gets her foot stuck in the toilet when she climbs in the bathroom window. Unable to free herself, she remembers a time when she was fiercely independent. When Richard and Barb find her, she's despondent, but her memory of her more independent days (and their teasing) inspire her to figure out how to get unstuck.
Matthew's relationship with Lucy is quickly tested when they move in together: her bizarre relationship with her dog and her obsession with how much space Matthew takes up makes them realize they can't be together. Matthew moves home and Christine is no longer alone.
Christine gets angry with Richard when Ritchie gets injured at a skateboarding party. It makes her even more overprotective, and, in doing so, she accidentally runs over Ritchie while he's riding his bike. Ritchie is unhurt, but Christine and Richard argue over who is the worst parent. They finally realize they've actually done a pretty good job.
Matthew dates the lunch lady from Ritchie's school. She's very boring, and he's insulted when she breaks up with him because he talks about his ex-girlfriend Lucy all the time.
Ritchie makes a new friend at school and invites him on a play date. He shows up with his mother, Francie, and Christine has to entertain her. Francie very quickly becomes relentlessly dependent on Christine, but Christine doesn't mind: Barb told Christine she 'needed a break' because Christine is too needy and Christine is enjoying being on the other side. It all gets to be too much when Francie asks Christine to give the eulogy at her grandmother's funeral. What does Christine do? She asks Barb to give the eulogy.
Matthew moves in with New Christine and Richard while the heater in his room is being fixed. It's starts off well, but it turns out New Christine is a perfectionist when it comes to homemaking and Matthew can't quite live up to all the rules.
Christine and the meanie moms are escorting the students on a field trip to the planetarium when Marley and Lindsay's water breaks. Christine takes them to the hospital, then tries to leave, but they insist she stay because she's their friend. The meanie moms are quite demanding, and Christine gets overwhelmed helping them so she calls Matthew. Matthew is tuxedo shopping with Richard, so he brings him to the hospital. Matthew can't handle them either, so Richard offers. Christine points out how useless he was when she was in labor, but he remembers things differently. Turns out, he's great with the meanie moms and Christine falls a little in love with Richard all over again. Richard feels the same way, but Matthew figures out a way to put an end to their renewed love.
Ritchie is excited when he's sent home from school because he has lice, however, Christine is furious. Christine decides to pull Ritchie from the school and send him to the local public school. Unfortunately, because its a charter school, he has to be admitted. When the family shows up, they look like the Addams family because of their hair treatment for lice. They don't get into the school and Christine has to return to the private school and eat crow to the Principal in order to get Ritchie readmitted.
Christine uses her expertise as a gym owner to help Matthew lose weight. In her attempt to help him, however, Christine is unable to shed the extra pounds she has put on herself.
To convince everyone she's fine with Richard's remarriage, Christine pretends she and her date, Todd (LEE TERGESEN) are in love. CONSTANCE ZIMMER appears as New Christine's sister.
Feelings are reawakened between Christine and Papa Jeff (SCOTT BAKULA) at Richard and New Christine's wedding, until Christine receives some shocking news. CONSTANCE ZIMMER and JAMES LESURE also guest star.