In Season 5 Wesley's Love Interest 'Fred' Burkle is killed so her body can by used by Illyria. In exchange for Illyria agreeing not to kill anyone, Wesley acts as Illyria's guide to this strange new world she's been reborn into. Angel flat-out asks Wes if he's in love with Illyria; he denies it adding, "But I do need her." Wes does try to limit this trope — when Illyria offers to take Fred's form to understand human relationships Wes is outraged and refuses to speak to her for a while. Just before the Grand Finale, which no-one expects to survive, Team Angel spend their time doing simple things they enjoy. Wes on the other hand just tends to Illyria's wounds, and she once again offers to comfort him by taking Fred's form, but Wesley refuses because he knows Fred is gone and to accept anything else would be a lie. "And since I don't actually intend to die tonight, I won't accept a lie." When Wes receives a fatal wound, Illyria asks "Do you want me to lie to you now?" Wes agrees, and Illyria morphs into Fred, telling Wesley she loves him and that they'll be together in the afterlife.
The second Conduit is this to the first one.
Battlestar Galactica (Classic): Lighthearted example: In the original show, the robotic-drone daggit ((AKA a dog)) replica Muffet II was created as a replacement for Boxey's pet daggit Muffet who was killed by falling debris during the attack on Caprica.
This is the origin of the Cylon Centurions. Replace a goldfish (namely your dead daughter), set in motion the end of your civilization.
Oh, and Cavil was made in the image of Ellen's father.
All the human models seem to be Ellen and Tigh's replacement children and/or the Final Five's replacement PEOPLE.
Being Human: This trope is discussed by name - and involving an actual goldfish - in one second series episode.
The Big Bang Theory: Raj becomes closer friends with Stewart, the local comic book shop owner, after his Heterosexual Life Partner Howard Wolowitz gets married and goes to space. At one point Sheldon even refers to him as "fake Wolowitz" and insists that if Stewart if is hanging around the group more now he has to act just like Wolowitz. It's worth noting, however, that Stewart is also a very lonely individual and was more than happy to be recognized as the replacement so long as he gets companionship out of it.
Black Mirror: In the episode Be Right Back there is a whole online service devoted to replacing loved ones with an online relationship. And if the client wishes it; to have a full replica of the person.
The Borgias: Has Ursula Bonadeo, Cesare's love interest. He meets Ursula while visibly distraught during his sister Lucrezia's wedding, and essentially transfers his obsession with Lucrezia to Ursula. They share the same hair color/clothing styles, and both suffer from abusive husbands. Fans love pointing out how many of Cesare's conversations and even poses with Ursula mimic his interactions with Lucrezia.
The Buffybot doesn't start out this way, but after Buffy dies at the end of Season 5, one of the series' more poignant scenes features Dawn, missing her big sister, lying down next to the Buffybot and cuddling with the robot as it charges. Furthermore, in the same episode we see Giles trying to instruct it in Eastern philosophy during a sparring session.
Well, it actually sort of did start out that way, since it was built by Warren to be Spike's Doppelgänger Replacement Love Interest for Buffy who rejected his advances. Ironically after Buffy's death Spike can't stand to look at the Buffybot, and is disgusted when it obeys its earlier programming and tries to flirt with him.
Caprica: By the series finale, Daniel and Amanda Graystone have fully accepted the Zoe avatar as a substitute for their dead daughter (it helps that she possesses almost every memory that the original Zoe did), even providing her with a physical body so she can interact with the real world.
Dark Angel: Max is eventually informed by her former commander and father figure, Donald Lydecker, who had been hunting her and the other escaped X5s for a long time, that her genetic code contains DNA preserved from his dead wife. She is not an exact duplicate, "more like inspired by".
Has Shibolena, the android created in the shape of Dr. Hinelar's daughter, Shizuka.
Earlier than that, Choudenshi Bioman had the Black Prince, who was created in the shape of Doctor Man's son, Shuichi. Subverted in that Shuichi is actually alive, and met the Biomen after the Black Prince's demise. In fact, his appearance revealed that Doctor Man was oncea man.
And in one episode of Taiyou Sentai Sun Vulcan, Black Magma builds a robot replica of a scientist's dead daughter in exchange for his creating a lethal poison. The robot eventually accepts the scientist as its father and refuses to kill him when ordered to, leading the villains to destroy it.
Dirk Gently: Subverted Trope, where Professor Jericho has built a voice-responsive Robot Kid named after his daughter, who died in a car crash. However the real Elaine is not really dead but in a coma, Jericho is in denial that she's not going to recover, and far from transferring his affection to the robot, he's planning to sell her to China.
K9 was created by Professor Marius to replace the dog he couldn't take to his new home, Titan.
Also used with K9 in a later episode; after bidding farewell to Leela and K9, the Doctor immediately takes out a box marked "K9 Mark II".
And again in the new series, with K9 Mark IV being given to Sarah Jane Smith immediately after the heroic sacrifice of K9 Mark III.
Also in the Doctor Who episode Journey's End, when Rose must return to the alternate universe she was trapped in for two years, The Doctor gives her a replacement copy created when he transferred his regeneration energy into his severed hand, and Donna touched it, creating a second Doctor
Not to mention, the whole ending of "Doomsday", where Jackie becomes alternate-Pete's replacement for alternate-Jackie, and alternate-Pete becomes Rose and Jackie's replacement for Pete, and Mickey becomes the replacement for Ricky (alternate-Mickey).
Also, in the Doctor's Daughter, Jenny could be seen as a replacement goldfish to his family on Galifrey, which he remarked had died previously. Though as far as the Doctor knows, he's lost Jenny as well, so not much of a replacement.
In the case of the First Doctor, he picks up Vicki, an orphaned young girl, immediately after losing his granddaughter Susan, and treats her like a surrogate. A couple of stories after Vicki leaves he picks up Dodo, who he takes an immediate liking to on account of her physical resemblance to Susan, despite her unusual stupidity.
The trope is frequently invoked any time the Doctor gets a new companion. The Doctor either expressly says he needs someone else with him or denies that the new companion is replacing the old. This trope is usually averted or subverted when the Doctor develops a genuine relationship with the new companion.
In the episode "Man on the Street" (1x06), an Internet billionaire, Joel Mynor, uses Echo as a replacement for his dead wife Rebecca, but only once a year - the anniversary of her death in a car crash on her way to the new house Joel bought when he finally hit it big in business. Later, toward the end of "A Love Supreme" (2x08), Echo - who now can control the 40 personalities in her brain - briefly becomes "Rebecca" for the last time to give her blessing to Joel's remarriage.
In the episode "Instinct" (2x02), another Rich Dude rents Echo as a longer-term replacement for his wife and mother of his infant child; again, the client's wife had died too young (in this case, of complications from the birth).
Elvis And Slick Monty: Parodied. In one episode, Slick had to get a literal replacement goldfish after Dr. Leonate Elvis's old one while he is away, only for Leon to eat the replacement goldfish itself. With no time left to get another one, Slick stuck Dr. Leon's hand into the bowl. Elvis was fooled.
Eureka: In the second episode, it is revealed that a scientist (after his wife leaves him) makes a clone of his wife and acts as if she had never left, even having a child with the clone.
Fringe: Peter Bishop. The Peter from our universe died as a child and in his grief, Walter, his Mad Scientist father, dragged an alt-reality Peter into our world as a replacement.
The recently widowed Scott latches onto an old friend of his late wife, ignoring all signs that she's up to no good. Not until best friend Lucy produces undeniable evidence that she's a scam artist does he finally admit that he's been projecting his memories of his late wife onto her.
Similarly, Sonny fell for undercover FBI agent Hannah Scott because of her eerie resemblance to his late wife Lily (killed by a car bomb meant for him) and his late lover Brenda (killed in an entirely unrelated incident, but he blames himself anyway).
Stefan initially seemed genuinely interested in Katherine, but bit by bit, began to mold her into the image of his lost love Laura.
Hamish Macbeth: The episode "Wee Jock's Lament" has the title character's dog, Jock, run over and killed at the beginning of the episode. At the end of the episode, he ends up receiving another dog of the same breed as a reward for solving the crime of the week — and he names it Jock.
Knight Rider: A really unpleasant twist for Michael Knight occurs in the second season episode "Goliath". Turns out he's the replacement for his benefactor's rotten-apple of a son Garthe.
Law & Order: Criminal Intent: In the episode "Saving Face," a wealthy couple have a new kid to replace their treasured son, whom they view as having possessed Marty Stu levels of perfection. Their daughter is perpetually The Unfavourite her entire life and eventually resorts to crime in her desperation to gain her parents' approval.
Law & Order: Special Victims Unit: In the episode "Locum", a couple is revealed to have adopted a orphan girl simply because she looked almost identical to their biological daughter who was lost years before. To make the newly adopted kid look as much like their lost child as possible, the parents (mostly the mother) forced the 8-12 year old to wear the girl's clothes, dye her hair, and even get a nose job. The kicker? The biological daughter is found by the police alive and, at the end of the episode, is returned to her parents as the replacement daughter watches on.
LOST: Juliet is made into this twice, both times by Ben. The first time, he tries to use her as a replacement goldfish for Jack's ex-wife Sarah to further his Mind Screw on him. Then before that, for himself as a replacement goldfish for his MIA childhood sweetheart Annie.
Malcolm in the Middle: Dewey did this in one episode with, indeed, a goldfish. Subverted Trope, since Dewey kept replacing the goldfish in order to fool his parents into believing he could reliably care for a pet so he could have a dog.
Monk: Featured a literal replacement goldfish. Natalie's daughter, Julie, had a goldfish given to her by her father who was subsequently killed in combat. Natalie repeatedly replaces the goldfish so that the daughter won't lose this emotional link to her father. Unfortunately, she does this well beyond the average lifespan of the domestic goldfish, which Julie's science teacher notices.
NCIS: Tony has a goldfish named Kate, after a teammate who died early in the series.
Now joined by one named Ziva.
Newhart: "Hi. I'm Larry. This is my brother Darryl, and this is my other brother Darryl." You didn't even have to be adopted to be a Replacement Goldfish.
The Office (US): Following the one year Time Skip in the Grand Finale, we find out that Phyllis has been offering sweets to the new black employee who replaced the now-retired Stanley. During one of her confessionals, she then reveals that she's purposefully fattening the new kid up in hopes that he'll one day resemble Stanley, who she misses dearly.
One Foot in the Grave: Patrick adopts a dachshund after Pippa miscarries following a road accident. Pippa correctly points out that the dog is his "baby substitute".
Revolution: In episode 10, it is revealed that Miles is this for Bass Monroe, replacing his entire family. Deconstructed Trope, because Monroe developed an unhealthy borderline erotic fixation on Miles, and when Miles betrays him (expanded on in the first season finale) as well as disowns Monroe for ever being family, Monroe just loses whatever pretense of sanity he had. Monroe failed to realize that Miles is not some pet, but a human being with his own feelings.
The Sarah Connor Chronicles: It is hinted that Allison Young and Future!John have a relationship, and that Cameron may be her replacement in more ways than one....
Scrubs: J.D. and Turk are very attached to their stuffed dog Rowdy, which Carla hates. As a favor to Turk to make up for hurting his feelings by insulting the dog, she offers to get him cleaned. On the way home, she loses the dog by not tying it to the top of her car securely enough. She then attempts to find a replacement.
And then the ruse falls apart when the real Rowdy is found... and J.D. and Turk are thrilled because now they can both have one.
Sliders: A mad scientist in one episode was, in fact, his robotic replica without even knowing it.
Smallville: Adrian Cross and Gabriel Grant were both clones of Lex's deceased brother Julian. Lex shot the first and hired an assassin to kill the other. In the same episode.
Dr. Noonien Soong replaced his wife with an android (with her memories) despite the fact that she was going to divorce him. He went to such extreme measures to make her seem human, even the most advanced technological equipment and everyone she ever met, except Data, couldn't tell the difference.
Actually, Soong stated in a recording that he didn't just replace his wife; he transferred her whole mind into an android body while she was in a coma. Another cyberneticist, Ira Graves, did this with Data in a previous episode in order to cheat death. Soong's wife was still the same person, but had unknowingly become a Tomato in the Mirror who would never find out.