Ethan of Athos: Terrance brings his wife's corpse to the best scientists money can buy and asks them to revive her. They can't, but offer to create a clone identical to Janine in looks, personality, and mannerisms - perhaps even with a few improvements. Terrance declines, but he does have the scientists splice her DNA into donor ovaries so that he can have thousands or millions of Janine's babies.
Averted with prejudice in the same series's Mirror Dance, by both Miles's and his mother Cordelia's emphatic refusal to treat Miles's clone Mark as anything but Miles' brother. One of the reasons for this is that in the setting, most civilized societies with cloning technology treat a clone as legally either the child of the person who originally commissioned its creation, or the sibling of the clone's genetic progenitor.
In Forever Amber, the heroine Amber marries the creepy, elderly Earl of Radclyffe. It turns out he's attracted to her because of her resemblance to his long-lost love, Judith, and even has Amber wear Judith's wedding gown. Neither Radclyffe nor Amber realize that Judith was Amber's mother.
In Double Identity, Bethany was cloned from her parents' deceased daughter Elizabeth.
Inverted and played straight in Dave Duncan's Strings.
In one of James Herriot's Yorkshire vet books, he is trying to clip the beak of a bird (a needed procedure for the health of the bird) belonging to an old, blind lady who is easily upset. The bird dies, and he stares with horror at it. He and the caretaker conspire to buy another exactly like it. The lady accepts it as the original. except she mentions the bird never sang so much before- clipping its beak did wonders!
My Sweet Audrina by V. C. Andrews has an odd twist to this trope. Audrina, the title character, is a girl living in the constant shadow of her elder sister who had died nine years before she was born, and her parents have absolutely no qualms about letting their daughter know that she was born and raised for the sole purpose of replacing her dead sister. But as it turns out, Audrina and her sister are one and the same. Audrina had a very sheltered life and, on one of the few times she was allowed to walk home without an escort, she was attacked and raped. She managed to get home safe and sound, but after a few suicide attempts her father forced her into electro-convulsive therapy in order to erase her memory of the event. Many of her supposed mental problems, as well as the personality defects her parents are constantly trying to fix, are caused by the initial treatment and the constant confusion her parents keep her in to maintain the amnesia. And, as it turns out, that's only one of her problems...
V. C. Andrews is very fond of this trope. Another example is in the Heaven series, in which the titular character dyes her hair blond to resemble the mother she never knew. Problem is, this causes her father (who already seems to be displaying an unhealthy interest in her) to confuse her with her mother (whom he raped, resulting in Heaven's birth), to the point where he tries to force himself on her. This is still a subverted example, as she chose to dye her hair rather than being pressured into it, but in the next book, her daughter is pressured into doing this by her grandfather (she's living with him, recovering from injuries sustained in the car accident that killed her parents). Sure enough, she nearly becomes his victim as well.
In the "Gemini" series, the main character, Celeste, is forced to take on the identity of her dead twin brother by her mother. Yeah.
Melody Logan in the "Logan Family" was a victim of this in regards to two characters; her cousin Laura and her mother Haille. Her Aunt Sara expected Melody to dress and act as Laura did, and treated her more like she was her daughter Laura and not her niece. Sara's husband Jacob and Laura's twin brother Cary were aware of what Sara was doing and despised Melody for it though Cary later fell in love with her. Because of her strong resemblance to Haille, Melody also faced considerable derision from the Logan Family because of Haille's Black Sheep status and the family merely transferred their hatred for Haille onto Melody.
In Dan Abnett's Gaunt's Ghosts novel Only In Death, after Caffran's death, Dalin Criid is slotted into his father's place in the Ghosts. He bitterly resents it but is aware that he can do nothing to stop it.
Elizabeth-Jane Newson/Henchard in The Mayor of Casterbridge.
Harry Potter to Sirius Black. Harry's strong physical resemblance to his father James makes him a substitute for his best friend when Sirius escaped prison. This causes some tension between the two in the text when Harry is revealed to be less daring than James and Sirius is unable to handle it appropriately (saying things like "you're not so like your father at all" and "the danger is what would have made it fun for James" (paraphrasing)), and is reflected also in the film version when Sirius actually calls Harry by James' name in the battle scene where he dies. This Replacement Goldfish situation is also what prevents Sirius from being the father figure that Harry desires, and Harry from being the best friend that Sirius desires, neither are able to fully transition into the Godfather/Godson relationship because of their inability to get past the physical similarities that James and Harry had. Harry can't be the James that Sirius remembers because he never knew him, and Sirius can't be the father that Harry craves because he's trapped by the trauma of his youth.
And when Cersei gets separated from her brother Jaime, she uses her cousin Lancel as one of these. Complete with sleeping with him.
Also, Cersei's marriage was doomed as Robert Baratheon treated her like one for his lost love, Lyanna Stark.
Daenerys is one for Jorah Mormont's estranged wife, Lynesse Hightower.
Daenerys herself has Daario Naharis to replace her dead husband Khal Drogo, and her three dragons to replace her miscarried son Rhaego (this miscarriage left her infertile).
Jon Connington sees Aegon VI Targaryen as a replacement for his dead friend (and possibly more than that), Aegon's father Rhaegar.
Ned Stark oddly sees himself as this, as both his title and his wife had been intended for his older brother Brandon, who was killed.
In a very screwed-up version of this trope, Theon Greyjoy ends up being made into a replacement for Ramsay Bolton's servant Reek, via horrific torture and mental condition.
In Jessica, Ruthie seems to have a rather odd version of this. Her Imaginary Friend, Jessica, is her constant companion, always eager to play whatever game Ruthie devises and willing to take the blame for Ruthie's actions. Ruthie's parents are unamused and do not play along. Shortly before starting kindergarten, they suggest that Jessica should stay home. Ruthie, of course, takes her along anyway. After spending the majority of the day homesick and unhappy with only Jessica for companionship, Ruthie is approached by a girl volunteering to be her partner. Ruthie, unsure, brightens up considerably when the girl's name happens to be Jessica. Soon they are best friends, illustrations showing them happily doing all the activities that Ruthie and the first Jessica enjoyed.
In Edith Pattou's East, main character Rose was born to replace her dead older sister Elise, their mother's favorite of her (altogether) eight children.
In the Dune series, Duncan Idaho (who was killed in the first book) is eventually resurrected as a series of clones (which become pretty much disposable at one point). Eventually, the Idaho clones learn to awaken their latent memories of the past.
In the first book, Paul's first son - Leto II - is killed by the Harkonnen. In Dune Messiah, he has a another son and names him... Leto II.
Rebecca, by Daphne du Maurier, is an inversion of this. The second Mrs. de Winter spends most of the book failing to live up to the memory of Rebecca, her husband's first wife, who had drowned accidentally. She is explicitly told, often, that she doesn't measure up, by Mrs. Danvers, Rebecca's personal maid. The second Mrs. de Winter becomes more and more desperate in her attempts to live up to Rebecca's memory, because Mrs. Danvers has her convinced that that is what Maxim, her husband, wants. Just when the second Mrs. De Winter (she is never given a first name, and the book is a first person narrative) is near a breakdown, and Mrs. Danvers suggests that she throw herself out of a window, it is revealed that Maxim never really loved Rebecca, and in fact, came to hate her, because she was cruel, cold, manipulative, and unfaithful. Not only that, she had taunted him one night until he murdered her, by telling him she was pregnant with another man's child, which she intended that he would support. It doesn't end there, and Maxim is vindicated, so they can go on with their lives together.
In the novel Skinned, if a person dies but their brain is intact, the brain is scanned and the information is placed into a human-like robot body. Sometimes a person will choose to have it done to themselves. The main character of the book, Lia, is "killed" in a car accident, but her parents choose to keep her around as an android. Needless to say, this causes many emotional difficulties for both the now-robot Lia and her family.
In the German novel The Adopted Room by A. Michaelis, 11-years old boy Achim is adopted by a family. He later discovers that they had a son called Arnim who died in an accident when he was 4 - and they were born very close to each other. He contemplates that this is the reason he was adopted by them, despite having asthma.
At least twice in the Sweet Valley High series, Steven ditches his girlfriend Cara to pursue girls who resemble his dead girlfriend Tricia. To make matters worse, he refuses to see either girl as her own person and instead tries to mold them into Tricia's image—the food they eat, places they go, interests that they have. Not until one of the girls finally blasts him for this and declares that she deserves better than being used as a substitute does he finally realize how unhealthy his behavior is.
Daphne in The Golden Oecumene made a replacement for herself as a last gift to her lover before retreating into a Lotus-Eater Machine, making its personality an exaggerated parody of everything she thinks her lover wanted in her. Cloning Blues are touched upon, but the duplicate eventually develops its own sense of selfhood—and in any event, the lover is also an Artificial Human, having been created from a computer simulation.
The Berenstain Bears book "The Berenstain Bears Lose a Friend" featured a literal replacement goldfish like the Monk example below. Sister's goldfish died and Papa got her a lookalike to try to keep her from noticing and getting sad. It only worked for a short time.
Nurse Agnes Meredith in Septimus Heap starts hoarding dolls after losing her son Merrin in the first book - after all, with dolls you at least know what you are with.
Descarta of Within Ruin is originally one of these for Virgil's first love Ankaa. However he comes to love her for herself and decides not to put Ankaa's soul into her has he originally intended. Descarta is completely taken surprise by this revelation.
In The Hunger Games, Katniss can't help but see her little sister Prim in Rue, both being the same age and roughly the same size. When Rue was dying, Katniss actually calls her "Prim" in her thoughts before correcting herself.
In Peter Dickinson's book Eva, scientists have developed a procedure where the neural patterns of one creature can be 'regrown' in the brain of another creature, thereby preserving the mind. One of the scientists is in a horrible car accident with his wife and daughter. When his daughter is left shattered and in an irreversible coma, the procedure is done on her, placing her mind in the body of a chimpanzee. It's a roller coaster from there.
In Fate of the Jedi, Abeloth tried to force Ben Skywalker and Vestara Khai to take the place of The Son and The Daughter, whom she had once been The Mother to back when she had been mortal.
Replacement Goldfish: The Rifter: John/Jath’ibaye took up with the young Ourath because Ourath reminded him of Ravishan who was dead, even calling him by the wrong name sometimes. Not only was it not a satisfactory relationship, but Ourath conspired to murder Jath’ibaye. Jath’ibaye, with his habitual sense of guilt and responsibility, wonders if Ourath would have been a better person if he’d had a lover who appreciated him for himself as his first relationship instead of Jath’ibaye.