Oscar Madison (Matthau) is a divorced sportswriter who lives in a spacious but horrifically messy apartment. He hosts a weekly Friday night poker game, which includes as one of the players Felix Ungar (Lemmon), a persnickety writer for TV news. Felix is in a state of grief and despair, his wife Frances having just left him. After Felix nearly kills himself by jumping into the river, Oscar takes him in. Comic situations ensue as super neat-freak Felix and Oscar the slob irritate each other.
Matthau was reprising his role from Neil Simon's play, which had featured Art Carney as Felix. One of many many adaptations of the play, including a popular TV show that ran from 1970 to 1975 with Jack Klugman as Oscar and Tony Randall as Felix, a 1980s Race Lift TV show that featured Ron Glass fresh off of Barney Miller, and another TV adaptation in The New '10s that featured Matthew Perry as Oscar. Thirty years after the movie, Lemmon and Matthau reprised their roles in a sequel, The Odd Couple II.
- Accidental Misnaming:
- Part of the spousal relationship between Oscar and Felix is shown by Felix sometimes calling Oscar "Frances."
- Oscar and Felix keep getting the names of the Pigeon sisters mixed up. Even in the end credits, the names have to be switched around.
- Adopted to the House: Oscar invites Felix to move in with him after his wife kicks him out, and soon comes to regret it.
- All Women Are Lustful: Gwendolyn and Cecily are pretty clearly looking to get laid, dropping deliberate comments about how they're beating the Heat Wave by standing in front of their refrigerator in the nude. This is why Oscar is so enraged when Felix gets maudlin and ruins the mood.
- Bikini Bar: In the opening montage Felix wanders into your standard 1960s movie Bikini Bar, with go-go dancers in bikinis, while walking around after his wife throws him out.
- Book Ends: Begins and ends with the gang trying to play poker but getting worried that Felix might kill himself.
- Camp Straight: Felix, although apparently heterosexual, is quite effete.
- Character Development: By the end, Felix has grown out of his despair at getting divorced, and can face the prospect of a call from his soon-to-be-ex-wife with equanimity. Oscar for his part is not as much the filthy slob, telling his poker buddies to be careful with the cigarette and cigar ash as they sit down to play.
- *Crack!* "Oh, My Back!": Felix is hiding in Oscar's bathroom after being kicked out by his wife. Terrified that he's going to attempt suicide, Oscar and the other poker players break into the bathroom, hitting Felix with the door, who proceeds to moan about his back throughout the rest of the scene.
- Deadpan Snarker: Oscar has most of the best lines.Oscar: Let's play cards, and please hold them up. I can't see where I marked them.
- The Eeyore: Felix is this for much of the first part of the film, due to being miserable over the breakup of his marriage. His attempts to make small talk with the Pigeon sisters reduces all three of them to a sobbing mess in the short time it takes for Oscar to prepare drinks in the kitchen.
- The Film of the Play
- The Ghost: Felix's wife Frances and Oscar's ex-wife Blanche. Often talked about but never seen or heard, but we do hear a loud click when Blanche angrily hangs up on Oscar.
- Hypochondria: Another one of Felix's neuroses. He thinks he's allergic to all kinds of odd things, including perfume.
- Instrumental Theme Tune: Composed by Neil Hefti. Used for the Klugman-Randall TV series as well.
- There are unused lyrics as well, written by Sammy Cahn.
- Joisey: During one of the poker games Vinnie mentions that he and his wife are "driving to Asbury Park for the weekend".
- After Speed lights up a cigar during the same game:Roy: Hey, you wanna do me a really big favor? Smoke towards New Jersey.
- After Speed lights up a cigar during the same game:
- Match Cut: From bowling pins falling to pool balls being knocked around as Felix and Oscar are out having fun (or, rather, Oscar is trying to make Felix have more fun).
- Men Can't Keep House: Oscar's apartment is just this side of a toxic waste dump. Felix, who averts this trope as much as it can be averted, makes the place over.
- Missing the Good Stuff: Oscar misses seeing a rare triple play at the Mets game when Felix phones him at the ballpark press box to inform him he's making franks and beans for dinner.Oscar: ARE YOU CRAZY? ARE YOU OUT OF YOUR MIND? TAKE YOUR FRANKFURTERS AND... (slams phone down)
- Neat Freak: Felix's problem, which irritates Oscar to no end and apparently is part of the reason his wife left him. The poker game breaks up after the other players realize Felix washed the playing cards.
- Newhart Phone Call: Felix talking to his ex on the phone.
- Odd Couple: Think so?
- Rooftop Confrontation: Eventually Oscar snaps, breathing fire and murder and chasing Felix around the building. He chases Felix all the way to the roof, where he manages to restrain from murdering Felix but does demand that Felix move out immediately.
- Roy expresses irritation with Murray's glacially slow card shuffling by snarking, "Aren't you the one they call The Cincinnati Kid?"
- Oscar compares Felix to Mary Poppins. Later he calls him the Wicked Witch of the North.
- The Pigeon sisters note that Felix is named like the cat.
- As Felix and the Pigeon sisters are sobbing over their respective divorces, Oscar emerges from the kitchen with the drink tray asking, "Is everybody happy?" Besides being a funny gag, this would have been recognized by older 1968 viewers as the catchphrase of '20s'40s bandleader Ted Lewis.
- "'Let it be on your head!' What the hell is that, the curse of the Cat People?"
- Suicide as Comedy: The film opens with a despondent Felix planning to jump to his death from a hotel room, only to throw his back out trying to open the window.
- Talk About the Weather: Felix derails all the sex banter between Oscar and the sisters by making an awkward comment about the weather.
- Video Credits: Clips from the movie of the main cast—Oscar, Felix, their poker buddies, the British sisters.
- Way Past the Expiration Date: It's poker night in Oscar's apartment, cigar smoke fills the air:Oscar Madison: I'm in for a quarter.
Murray: Aren't you going to look at your cards first?
Oscar: What for? I'm gonna bluff anyway. Who gets a Pepsi?
Murray: I get a Pepsi.
Oscar: My friend Murray the policeman gets a warm Pepsi.
Roy: You still didn't fix the refrigerator. It's been two weeks now — no wonder it stinks in here.
Oscar: Temper, temper. If I wanted nagging, I'd go back with my wife. I'm out. Who wants food?
Murray: What do you got?
Oscar: (checks plate of pre-made sandwiches) I got, uh, brown sandwiches and, uh, green sandwiches. Which one do you want?
Murray: What's the green?
Oscar: It's either very new cheese or very old meat.
Murray: I'll take the brown.
- You're Insane!: In the play, after Oscar snatches the plate of linguini and senselessly throws it against the kitchen wall:Felix: You are crazy! I'm a neurotic nut but you are crazy!
Oscar: I'm crazy, heh? That's really funny coming from a fruitcake like you.