When the IRS decides to audit Oscar and his ex-wife, Gaby, Felix offers to mediate between the contentious exes and suddenly realizes that he might be the reason Oscar was audited in the first place.

Felix forces Oscar and Emily to go on a date to get to know each other better in the hope that they’ll become friends. Also, Teddy agrees to help Dani with her first contract negotiation.

Oscar faces a personal dilemma when he dates a young nanny, Allyson, who works for his neighbor, Charlotte. Also, Emily forces Felix to participate in an activity she's interested in, for a change.

Things get out of hand when Felix begins to meddle in his friends' personal lives and hires a counselor to help resolve their issues. Among the problems: Teddy's wife Diane believes that he is cheating on her with Dani after he stays out all night and Dani's moving in with Emily has created friction over the way the apartment is decorated.

With the help of Murph, Oscar decides to throw a big party when Felix finally agrees to spend the weekend away. Also, Felix and Emily have their first sleepover.

Oscar attempts to impress Charlotte by purchasing a table for a fundraiser to benefit The New York Philharmonic. At the event, Felix reminds Oscar about the importance of being honest and Teddy introduces his wife, Diane, to Dani for the first time.

Oscar and Felix run a heated campaign for president of their building’s tenants’ association, but Oscar doesn’t fully realize everything the position entails.

After Oscar and Felix become obsessed with eavesdropping on their bickering neighbors, they try to subtly intervene and help them save their marriage. Meanwhile, Emily and Dani's friendship is tested when they train together to race to the top of the Empire State Building.

Oscar and Charlotte hit a speed bump when they hesitate to take their relationship to the next level. Also, Felix attempts to overcome his fear of dogs with Teddy's help when Emily regains custody of Biscuit.

Oscar reluctantly agrees with his agent that it’s time to shake things up on his radio show and allows Dani to have a bigger role after a rival host, Rich Eisen, taunts him. Also, Felix is eager to meet Emily’s mother, Judy (Joanna Cassidy), but things don’t go as well as he hoped.

Felix attempts to reverse Emily's birthday curse and plans a nice dinner to celebrate with friends. Also, Oscar and Charlotte face another obstacle in their relationship when Oscar meets Charlotte's son, Evan (Caleb Brown).

In an attempt to surprise Emily, Felix gets his learner’s permit and enlists his friends to help him learn how to drive. Also, Oscar is annoyed that Felix doesn’t ask him for help,

After Murph persuades Oscar to try online dating, Oscar finds himself on a blind date with Felix’s ex-wife, Ashley.

After their marriages fail, Oscar and his former college roommate, Felix, decide to live together.

When Oscar realizes he forgot Felix's birthday, he plans an impromptu surprise party.

Dani wishes she had a boyfriend for her high-school reunion so Oscar, Felix and Ted work on finding her a man.

Oscar learns that Felix was nationally ranked chess player as a child and convinces him to return to the game to make money. Also, Emily investigates why Felix is acting strange since he began playing chess again,

Oscar's dream comes true when he is asked to throw out the first pitch at a New York Mets game. Also, Felix surprises Oscar and invites his father to be there for the big day.

Felix offers his help when Oscar is hired to ghostwrite a retired baseball player's autobiography.

When Oscar and Felix attend the wedding of an old college friend, Oscar aims to reconnect with an old flame while Felix is determined to show his ex-wife that he’s a changed man.

Felix’s hypochondria kicks into overdrive when Oscar starts dating the most important person in Felix’s life – his doctor.

Felix convinces Oscar to appear on a sports television show against Teddy’s advice to stick with radio.

When Oscar feels threatened by Felix’s surprising performance on the softball field and basketball court, they agree to a decathlon to determine which one of them is the better athlete.

When Oscar and Felix make a trip to Ashley's to retrieve Felix's special pillow, a secret that he has kept from Oscar is revealed.

When Felix substitute teaches a yoga class, his teaching style rubs everyone, including Emily, the wrong way. Also, Oscar and Dani get trapped on a subway car, adding to their frustration about living in the city, and Murph asks Teddy to be his agent when he’s approached to be the spokesperson for a Norwegian health supplement.

Oscar becomes weirdly obsessed with living up to Murph’s reputation when he finds out that the girl he is seeing used to date the handsome ex-baseball player.

Oscar is forced to choose between his romantic plans with Charlotte and helping to save Felix’s relationship as Emily decides to extend her stay in London and Felix starts to fall apart.

When Oscar learns that his favorite hangout, Langford’s, is in financial trouble, he impulsively asks Felix to help save it, without considering the disastrous consequences. Also, Felix tries to make his mark on the restaurant when the owner, Fred Langford , puts him in charge for a few days.

Oscar sets out to prove to Charlotte how he's capable of being responsible when he volunteers to take her son Evan (Caleb Brown) trick-or-treating on Halloween, while Felix celebrates the holiday by leading the kids in their building on a haunted history tour.

Oscar reconnects with many significant people from his father's life when he agrees to carry out Walter's last request to spread his ashes behind the candy factory he once owned.

Dani's excitement at being promoted is cut short when Oscar tasks her with the daunting job of hiring her own replacement. Also, Felix tries to plan the perfect surprise after Emily admits she misses England.

After his arch enemy Rich Eisen receives a humanitarian award, Oscar is forced to give a speech and wants to roast him. Meanwhile, Felix tries to fast-forward through the five stages of grief following his breakup with Emily.

Felix goes into a frenzy when the responsibility of hosting the Unger family Christmas falls onto his plate after his perfectionist mother bows out. Meanwhile, Oscar tries to convince his roomie's mom to give her son a break.

Oscar arranges for Felix to replace him on any cultural outing that Charlotte has planned; and Emily recruits Dani, Teddy and Murph for help making 100 necklaces for an event.

Felix takes the first step in moving on from Emily by picking up a bartender named Natasha (Busy Philipps) and bringing her home for the night. It later backfires when Felix doesn't know how to have a one-night stand; Natasha starts to get attached and won't leave. Meanwhile, Oscar takes his relationship with Charlotte to the next level by asking her to leave her toothbrush at his apartment, after which they get into a conversation about their relationship and say "I love you" to each other.

Murph is hosting a new TV sports segment wherein Oscar is pitted against a penguin to pick the winners of hockey games. Oscar soon becomes the butt of jokes when the penguin's random picks (made by walking under one team logo or another) turn out to be more reliable than his. Elsewhere, Emily asks Felix to shoot photos of her for a jewelry website, but Felix misinterprets her verbal cues and thinks she wants to get back together with him.

Oscar grumbles when Felix helps Dani prepare for a choir solo and encourages the group to attend church to support her.

After a heated argument, Oscar and Felix decide it might be best to change their living arrangements and find new roommates.