Oscar's life seems almost perfect...sure he's divorced and his apartment is a mess, but he's the host of a well-known sports show, and is enjoying his bachelor lifestyle in New York City. That is until his college friend, Felix, shows up at Oscar's apartment having just been dumped by his wife. Oscar does his best to console his old buddy and get him back on the dating horse, but his attempts uncover just how unresolved his own feelings are about his ex.
Oscar Madison reluctantly agrees to let Felix Unger, his uptight former college roommate, move in with him after both of their marriages fail.
When Oscar is hired to ghostwrite the autobiography of a retired baseball player, Felix offers his “help” by advising Murph to go in a different direction, making Oscar’s job more difficult.
When Oscar realizes he’s forgotten Felix’s birthday, he pulls together a last-minute surprise party in his honor in an attempt to impress Casey.
When Dani reveals she’s depressed that she’ll be the only single one at her high school reunion, Oscar and Felix each put their distinctive dating strategies to work to help her find a boyfriend.
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 the IRS decides to audit Oscar and his ex-wife Gaby, Felix offers to mediate between the contentious exes when he realizes that he might be the reason Oscar was audited in the first place.
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 obsessed with living up to Murph's standards when he finds out the girl he is seeing used to date the handsome ex-baseball player. Also, when Emily volunteers to be a part of a historical reenactment on Ellis Island in order to spend more time with Felix, he is too busy preparing for his role to pay any attention to her.
After Oscar and Felix become obsessed with eavesdropping on their bickering neighbors, they try to subtly intervene and help them save their marriage. Also, Emily and Dani's friendship is tested when they train together to race to the top of the Empire State Building.
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 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.
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.
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 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).
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,
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.
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,
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.
In the third season opener, 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.
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.
Oscar tries to outsmart his nemesis, Rich Eisen, after he is forced to present him with a humanitarian award. Also, Felix experiences a range of emotions when he sees Emily at a restaurant.
Oscar and Felix seek the advice of a counselor in their apartment building to help overcome their issues. Also, Oscar's opinions on relationships, combined with Felix's meddling, complicates matters for all of their friends.
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.
To avoid a night of boredom, Oscar suggests that Charlotte take Felix out on their artsy cultural dates in his place. Also, Emily enlists Dani, Teddy and Murph's help when she has to produce 100 necklaces for an event.
Felix meets a fun-loving woman, Natasha, in a bar and takes her home for what is meant to be a one-night stand, and Oscar takes things to the next level with Charlotte.
Murph gets Oscar to agree to participate in a regular TV segment where he competes with a penguin at the zoo to predict the winners of hockey games. Also, Emily and Felix take their first steps to becoming 'just friends.'
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.