The Unwanted Spouse is a character, usually in an Accidental Marriage, Arranged Marriage, or Shotgun Wedding, who is completely unwanted by his/her spouse, so much so that it becomes a plot point.
This character can be heroic—unhappily married to a villain, and made so miserable by the marriage that she turns around and betrays him, joining the heroes—or villainous (often the case if she's the woman standing between the story's two main lovers).
This character is female more often than male.
Note that when an action hero's wife is like this, she usually ends up Dying for the Ship.
As far as Shampoo and Cologne are concerned, Shampoo is already married to Ranma per the traditions of her village (he defeated her in a fight), all they need is to have an official ceremony for him to admit it too. Shampoo even outright states that they're married in her home village's newspaper.
Urusei Yatsura, another series by Rumiko Takahashi, centers on a young man who accidentally marries an alien princess. He wants someone else. Anyone else.
The Anime Final Approach goes beyond using this for characters — it actually uses it as plots.
In Rizel Mine, the main character is the one with an unwanted wife. He is 100% positive that, no matter what she says, he never got married to anyone.
In Gankutsuou Eugenie warmed up to the idea of being in an Arranged Marriage with Albert, but her father eventually decided to cancel the engagement and arrange for her to marry Andrea instead, whom Eugenie did not like at all. Not to mention that he's her half-brother.
Used for laughs in Baka and Test. Shouko repeatedly tells her former Only FriendYuuji that she wants to marry him, and tries forcing him to sign marriage papers, and threatens to kill/hurt him if he refuses. She often goes into Yandere/Clingy Jealous Girl mode if other girls are around him, or she feels he's getting a little too friendly with male friends.
Asayo Katsuragi from Sakura Gari is a very tragic case. Not only her husband Tomohiko is obsessed with lead male Souma, but he actually is veryabusive to her. And it's hinted that theirs was an Arranged Marriage since her father is the onwer of the hospital he works in.
King Hodr to Sigyn in Break Blade. Unlike most examples, Sigyn doesn't hate her husband, but married in order to make his best friend, Rygart, the one she actually loves, to do something about it. She tried to love her husband at one point, but failed to. Hodr, despite that he clearly loves her, knows full well she thinks of him as nothing more than a friend, which is what helps him agree to a divorce.
Ava Lord in Sin City starts off hating her mafia-tied husband and begs Dwight to do something about it. He does but it turns out to be a setup for Ava to inherit her husband's estate.
In Nexus The entire focal point of Jack and Knock Out’s bond was that it was an accident. Jack even tries to figure out a way to break it without killing himself.
In the Rumpelstiltskin retelling The Dressmaker Queen, the main character Jenny Thompson is forced into an unhappy marriage with the cruel King Gray. He returns to his many mistresses, only wanting Jenny to pump out an heir as quickly as possible. She's trapped in an unhappy marriage, unable to be with anyone else.
Played with in The Dark Knight fanfiction Question of Honor where Bruce marries a friend to get her out of her wartorn homeland. They only plan to stay together long enough for her to earn a right to stay in the States then get the marriage annulled. As he's still Batman, he doesn't have much to do with her at first until they do manage to fall in love.
Isabella of France falls (somewhat) into the heroic category in Braveheart when her awful marriage and clear unwanted status leads her into the arms of William Wallace...and into literally bitching Longshanks to death at the end of the film.
Lindo is put into an Arranged Marriage at the age of 16 to a 12-year-old boy. Neither of them wants the other, and the situation is ultimately resolved quite humorously.
Ying-Ying, on the other hand, is the abused and unwanted wife of a man she thought she'd be happy with.
Wyatt Earp's laudanum-addicted wife in Tombstone is another heroic example.
This was essentially the plot of the Eddie Murphy film Norbit.
Sita in Deepa Mehta's film Fire. The movie opens with her on the honeymoon of her arranged marriage to Jatin, who remains involved with his girlfriend Julie. The trope also manifests, albeit with a twist, in the character of Radha - her husband loves her but because she's infertile and he's deeply religious, refuses to have sex with her and pretty much keeps her around to test his devotion. He doesn't want to get rid of her, but she's deeply unhappy that he doesn't want her as a wife.
The Roseanne Barr comedy She Devil is a revenge story from the perspective of the Unwanted Spouse.
Carry On Henry posits that King Henry VIII (Sid James) had another wife (Joan Sims), a garlic loving wife he alternately wanted and unwanted as the political climate changed around him.
Abusive, controlling, big baby of a husband Earl in Waitress. The whole movie is about the protagonist trying to get away from him.
And then there's Du Chaillu, who declares herself to be Richard's wife in the second book (part of a Prophecy), and follows him around in the fifth book.
In With a Tangled Skein, we have a male example. Niobe has an Arranged Marriage to Cedric, a handsome, strong and highly intelligent man who is a few years younger than she is. Due to his youth, she is not at all happy. Later, she completely changes her mind about him.
Mr. Rochester's literally insane wife in Jane Eyre.
In the novel The Princess Bride (rather than the movie), Prince Humperdinck is marrying Buttercup purely because he's going to be king and he'll "have to." In both the book and the movie, he's looking quite forward to killing her on their wedding night. Give him credit, in the book he intended to marry the princess of Guilder, but she turned out to be bald.
A Rare Male Example exists in the Harry Potter series, though more implied than actual. Rudolphous Lestrange is so unwanted by his wife, Bellatrix (who, according to Word of God, is actually in love with Voldemort) that he only appears during the trial in Harry Potter and the Goblet of Fire, along with his brother, Bellatrix and Barty Crouch Jr. but he's so unimportant that the narration never even tells us which Lestrange man he was, and he has no lines. Judging by the fact that the Blacks are aristocratic pure-blood fanatics it was probably an Arranged Marriage.
A couple of unwanted marriages are in A Song of Ice and Fire: Cersei and Robert, and Sansa and Tyrion. The former fits better, since they actively hate each other. In the latter example neither want it, although Tyrion is willing to try and make it work while Sansa just retreats behind her Stepford Smiler mask. In the backstory Aerys and Rhaella Targaryen were also this in addition to being brother and sister forced to marry to keep their bloodline pure, and while there was no love lost between them on their wedding day it took Aerys going insane to really push it into Domestic Abuse territory, and Jaime Lannister recounts how Aerys would viciously rape her after he had burned someone and poor Rhaella looked like she'd been savaged by an animal afterwards.
Sarima in Wicked: The Life and Times of the Wicked Witch of the West.
This one works both ways. They were promised to each other as children without even meeting each other, so she doesn't really want Fiyero either.
The Bible: How's this for an example? You get a guy named Jacob who is working for his uncle Laban. (You probably see where this is going, don't you?) He notices his daughter Rachel, who is quite beautiful...enough so for Jacob to offer to work seven years for Laban in order to marry Rachel (don't ask). He does the work, gets married and learns (after the fact) that he just got hitched to Rachel's decidedly less attractive sister, Leah. And then he works seven more years to get Rachel.
In The Emigrants this trope is the reason why Jonas Petter emigrates to America.
In the Horatio Hornblower series, the main character marries Maria, a girl he considers a bit silly and overly emotional, out of guilt, because he can't bear to hurt her feelings by turning down her largely unwanted affections. He spends as much time at sea avoiding her as possible and sets himself up for misery at home by never once correcting her on any of her habits that annoy him, such as calling him "Horry" or cooking food he doesn't like.
Faye Weldon's novel, 'The Life and Loves of a She-Devil' (source of the Roseanne Barr movie mentioned, and an English miniseries with that title), tells the sometimes funny, often disturbing, story of the title character's revenge on her husband.
In Thorn In My Heart, based off the first part of the biblical story of Jacob, Jamie McKie's uncle Logan pulls a Bride and Switch on him, getting the Church Council to declare Jamie legally married to Logan's elder daughter Leona rather than her sister Rose. Jamie's initial reaction is to ignore Leona completely, even after she discovers that she is pregnant with his child. Jamie eventually moves past his anger and learns to love Leona. However, at the end of the book, Rose's machinations cause the Church Council to reverse their decision and declare Jamie married to Rose and not to Leona. The second book, Fair Is The Rose, opens with Jamie treating Rose with just as much coldness and anger as he had initially treated Leona with.
Live Action TV
In Everybody Loves Raymond, Frank and Marie make you wonder if they ever even LIKED each other. The funny thing is, they still do. They just "made room" for hate in their relationship and, in fact, were separated for a time.
Saffron of Firefly is one of the rare women unwanted by a protagonist, due to the protagonist not knowing about the wedding customs of the planet they were on and her stowing away on the ship. Mal Reynolds spends most of the episode desperately trying to unload her (Justified, however, when she turns out to be a villainous con artist that married him in order to steal his ship.).
Dr Robert Kelso's marriage to his (unseen) wife in Scrubs.
Bob Kelso even seems to do the same thing with his mistresses, or maybe that's a subversion.
Though to be fair, it appears he did love her at first, even writing a song about her when he was younger.
This was the basis of most of the comedy in Married... with Children, what with Al's dislike of his oversexed wife, Peg.
Maris on Frasier eventually turned into this before the divorce storyline.
Not sure if this counts, since she was supposed to be pure evil.
Londo Mollari of Babylon 5 is married to 3 women (via Arranged Marriage). Londo makes jokes about how his work on Babylon 5 keeps him away from his wives is a good thing. He is granted a divorce by the Emperor—two divorces, actually—and two constantly fawn on him to ensure that they won't get the metaphorical axe. They also plot to kill him. His first wife, Timov, doesn't participate in the scheming and is openly hostile—and in the end, Londo chooses to keep her, as he prefers her open hostility to their cloying faked affection. Also, she didn't try to kill him (in fact, she saved his life, but she never tells him that).
Jack Shepherd of LOST started off being wanted, but his lack of focus, constantly needing to "fix something" resulted in his wife leaving him for another man that sent him spiraling out of control, to the point he accused his own father of being the "other man".
Sam of Australian serial Neighbours was this to estranged husband Dan. Seemingly brought in for no other reason than to complicate his relationship with Libby, she hung around, trying to persuade him that they could give it another shot. Dan being the honorable man he is, agreed to try, but it was clear that, though he by no means hated her or wanted her to leave, he would have much preferred it if she had not come back. This is much clearer the second time it happens; after giving up and leaving for a while, Sam reappears heavily pregnant just in time to spoil Dan and Libby's upcoming wedding.
Charlie is this to Stella in The League of Gentlemen. Although he has grown to despise her too, the extent of her hatred (and verbal abuse) is much greater. While he still tries to make peace with her (especially in the Christmas special) she sees him as little more than a burden and never misses an opportunity to say so.
Poor Anne of Cleves on The Tudors. It's still not entirely clear what she did wrong that Henry took such a dislike to her, although most explanations hold that it was a portrait that Henry agreed to marry, and the real thing turned out to be uglier than the portrait.
In Real Life, while Henry may not have liked the look of her and did divorce her, she was arguably the best off of all his wives; he called her his beloved sister, loved her truly (brotherly love, not romantic), invited her regularly to the palace, and swapped cooks with her. They were dear friends for life. Considering the fates of Henry's other wives, Anne arguably got the best deal.
In The Caesars, Emperor Caligula makes his lame, stammering, unattractive uncle Claudius the unwanted husband of his attractive cousin Messalina. Claudius is thrilled at the prospect; Messalina, decidedly less so.
On Revenge, Daniel ultimately only married Emily because he thought she was pregnant. When he learned she wasn't, he shot her. She survived that and was able to use that to blackmail him to stay in the marriage until she decided she wanted it to end; she had only married him so she could frame his mother for her murder.
Regina married Leopold because her mother basically forced her to. After the marriage, it wasn't long before Regina manipulated someone into killing him.
The Dark Curse brought Charming and Abigail, who had previously called off an engagement because both loved other people, together as David and Kathryn Nolan. When the Curse started breaking, David found himself drawn to his real wife, and Kathryn eventually realized she wasn't happy in the marriage either; after the Curse completely broke, their marriage was never brought up again.
Meat Loaf's song "Paradise by the Dashboard Light". Long story short, he swears to a girl that he'll love her till the end of time so he can get some. Fast forward, and now he's praying for the end of time to hurry up and get here, because he can't stand her but he won't break his word.
And the girl apparently can't stand him either, so it's played straight on both sides.
There's also a Newfoundland song called "The Scolding Wife", covered by Great Big Sea, whose refrain goes:
And if the Devil would take her, I'd thank him for his pain,
I swear to God I'll hang meself if I get married again!
The 50% of Country Music that isn't composed of "She left me" songs seems to consist almost entirely of these. Example title: "How can I miss you if you won't ever leave" by the Shirtless Biddles.
"Why Don't You Get a Job" by The Offspring, quoted at the top of the page. The final verse tells about another, female, friend who has the same problem with her boyfriend.
My friend's got a boyfriend and she hates that dick She tells me every day He wants more dinero just to stay at home Well, my friend, you gotta say...
In Margin for Error, Sophie despises her husband and is desperate for him to grant her a divorce. Her husband's threats to turn her and her father over to Nazi authorities for execution are what keeps her from running away from him with her lover, Denny.
She's not so much unwanted as, when she forked over the Sapphire and said her mom told her to give it to the man she intended to marry, you were too young to really grasp what she was talking about. When she confronts you about it seven years later, you're not so much disinterested in marrying her as surprised she's in the Temple at all.
In Fallout 2, you can get a shotgun wedding. Your spouse is useless except as a very frail meat shield.
Subverted later Edgar was transmogrified into a hunchback, and had been kidnapped by Lolotte as a baby. Genesta transforms him into his true form, a handsome Fae Prince. In the seventh game, he's kidnapped and transmogrified again. After Rosella saves him, the pair wisely agree to a proper courtship before rushing into anything.
In Dragon Age II, a major plot arc begins from a dissolute husband seeking his runaway libertine wife. It's quickly apparent that they mutually unwant each other.
Henpecked Hou of Jade Empire only stays married to his wife because he's terrified of her. She's pretty much ruined his life. The Open Palm ending reveals that he manages to take a job as a deliveryman in a faraway city and leave her.
The Badass Preacher hires you to prevent this from happening in The Saboteur. To kill the Nazi General that was forcing a young French woman to wed him.
Matt Horner of Starcraft II accidentally got married to Mira Han after winning a poker game (he didn't know she was the stake). When Raynor meets her via videoscreen, Matt hides out of sight making very energetic "I'm not here!" gestures.
For her part, Mira seems very fond of Matt; of course, it's not entirely clear if this is genuine affection or if she just enjoys screwing with him.
In Final Fantasy X, Seymour asks Yuna to marry him. She agrees to it, but only to get close enough to confront him about murdering his father. Later in the game, he forces her to marry him while the rest of the party are held at gun point watching.
In samurai RPG Legend of the Five Rings, this is a disadvantage that characters can take. Considering that wives are in charge of the man's finances, this can be especially painful for male PCs, while the male domination of most marriages makes it physically painful for many wives. It's not a nice setting sometimes.
From Magic: The Gathering there's Kayla who became Urza's wife after he won her hand in marriage by winning a contest of strength with an automaton he built. He was more interested in the relics in her father's vault than her.
Hunding in Wagner'sRing cycle (Die Walküre), who is killed for the incestuous Siegmund/Sieglinde ship.
Happens in The Simpsons when both Homer and Flanders drunkenly marry two cocktail waitresses in Vegas and a waitress shows up in a later episode as an unwanted spouse.
The Powerpuff Girls has the Mayor's wife. Rarely mentioned and almost never seen, but on the few occasions she does come up it's made abundantly clear that the Mayor doesn't care for her much. He was willing to give her up to a bunch of thugs for them to spare Miss Bellum.
In The Critic, Jay was an unwanted spouse of his ex-wife Ardeth. She even admitted to his face about regretting marrying him during their wedding day.
In Moral Orel, Clay and Bloberta Puppington are in a completely loveless marriage that is explored in the third season. In the episode that explains the circumstances of them getting married, it's shown that Bloberta was desperate to be with someone and ended up with Clay after driving him to alcoholism by justifying to herself that he would need someone to help him. They cannot get divorced due to the hyper-Conservative environment of their town and in the epilogue it's hinted that they grow old and miserable together.
This is also Truth in Television: plenty of royal marriages were like this, the most recent example being Charles and Diana Windsor aka the Princes of Wales. He couldn't marry his long-time lover Camilla Parker-Bowles because she was a married woman and wasn't a virgin beforehand, she was a viscount's naive daughter who thought she'd become a full-blooded princess by marrying him, they got hitched and things progressively went From Bad to Worse.
Isabelle of France, mentioned above under Braveheart, was not averse to becoming queen of England, but with another king. Edward II basically ignored and humiliated her during their marriage, and he possibly/allegedly cheated on her with his squires and other (male) "friends". There are various theories that she may have murdered him, possibly in retaliation for this, though the popular story that the method of assassination was being buggered to death with a red hot poker has no basis in contemporary accounts.
And of course we have Henry VIII of England, who is infamous for the extremes he would go to in order to dispose of one unwanted spouse after another — so far as splitting with the Roman Catholic Church for refusing to grant a divorce and starting his own denomination in one case, and having the unlucky woman executed in two others.
Catherine the Great and her husband Peter III of Russia were this to each other, and Catherine eventually had him arrested and forced him to abdicate before he conveniently died in prison, leaving her in charge of the country, a position she held until her own death of old age.