Karen LeBlanc was born to Monique and Andrew, a politician and a scientist. A couple years after Karen, Blair was born, and the siblings despised each other from the start. At a point during the girls early teen years, Andrew cheated on Monique with single mother Dusty and fathered a daughter with her. Andrew and Monique divorced and Andrew married Dusty. The event caused more heartache within the family, and Monique was left to deal with her squabbling children. As a result of the divorce, Monique changed her surname and the girls to her maiden name Stradenflugen to spite Andrew. It's possible the trauma of the divorce is what caused Karen to become as vindictive and cruel as she ended up being.
Monique and the girls moved into the abandoned Goth house, and immediately made it their own. Blair took up painting in the attic, Monique filled the place with her gem collection, and Karen took good use of the large, supposedly haunted house to scare her sister at every opportunity. Karen was known for her popularity at school, both being the class clown and the "it girl". Blair is the complete opposite, a goth girl who keeps to herself. The clashing personalities caused more conflict between the sisters. As much as Monique tries to keep the peace, Karen couldn't help but feel as though Blair is the obvious favorite.
Soon, Blair began to get more popular when she started dating Kameron French-Frio, the son of Jared Frio and Molly French. Karen was jealous of this relationship as well as the school-wide attention Blair received because of it. After another massive argument between the twins, Karen planned an attack on Blair in order to get the message across that Blair needs to stay away from Kameron. While Monique was out at a work dinner, Karen scared and assaulted Blair savagely. Karen left Blair, expecting her to get up afterwards and fight back, but came back later to find Blair was still where she left her. Karen soon realized that she had killed Blair. Karen became upset and hysterical, she only meant to hurt Blair not kill her. Karen left the scene and hid, leaving Monique to return and find Blair's body dead on the floor.
When asked, Karen made up a story about a burglar coming in and attacking the girls, and Blair took the brunt of the attack. While some suspected Karen, Monique wholeheartedly believed that she had nothing to do with it and the case was dropped, the murderer never found. At one point after Blair's death, a burglar broke in and was interrogated over Blair's death and the "previous robbery". Despite Karen's best efforts to get the burglar charged for the murder in order to get the case done with, it was eventually proven it wasn't him by lie detector and the case remained unsolved. Monique's grief caused her to pass out at the funeral, causing Karen to feel immense guilt over what she did and briefly consider confessing. After a while, the family moved on from Blair's murder, and Karen continued her class clown demeanor, with no one knowing that Karen had murder on her conscience.
Karen graduates from high school with honors and was voted Most Likely to Take Over the World. After graduation, Karen joins the Criminal career path. Karen goes out to a nightclub, where she meets billionare vampire Thornton Wolff and after a few drinks she hooked up with him. Karen's tryst with Thornton was an unpleasant experience as she realized Thornton had become infatuated with her overnight and Karen realized would much rather start a relationship with his wife Morgana than with Thornton. Karen began to regret the encounter as she discovered her attraction to women in the past and realized she's a lesbian. When Karen tried to leave, Thornton got violent and locked her in his bathroom overnight. Karen spent the night in the bathroom, and in the morning Thornton once again got violent and attacked her. Traumatized, Karen killed Thornton, marking her second killing. A few weeks after the traumatic encounter, Karen discovered she was pregnant much to her dismay. Karen immediately decided she was unfit to be a mother and it wouldn't be fair to raise the baby, with Karen being a criminal with two murders under her belt and the baby having been conceived in a traumatic experience, Karen decides the child would benefit greatly from being raised by another family and decided to have the baby adopted.
Karen told her mother about her experience, but refused to name the child's father as if she did, she would likely be arrested for Thornton's murder. Monique is sympathetic about the circumstances, but tried to force Karen to keep the baby as a way for Monique to compensate for Blair's loss. Karen was adamant she wasn't keeping the baby, which made Monique upset as she realised that with Blair being dead and Karen not wanting children, Monique would never become a proper grandmother. Eventually, after realising how distressed Monique was making Karen, Monique agreed to let Karen give up the baby. Karen gave birth to a baby boy, and Monique instantly became smitten. Monique tried to adopt her grandson as her own, naming him Jacob Stradenflugen. Karen didn't want to be anywhere near the baby, as he reminds her of Thornton. After making Monique choose between Karen or Jacob, Monique chose Karen, and baby Jacob was adopted by the Vasquez family, Wendy and Bennie, and renamed Dustin. Karen said goodbye to Dustin and admitted that it's because she loves him that she has to give him up to a better life. After that, Karen simply tries to forget about the experience and begins dating her boss, Ayesha Ansari.
Karen started to feel as though with Ayesha, all her demons were behind her. She'd forgotten about Blair and Thornton, her son was happy with his adoptive family, and she had a stable job with a stable relationship. At a party thrown by Monique, Karen proposed to Ayesha, who accepted. They had a private wedding at a dance club. Karen and Ayesha enjoyed a brief but happy marriage, as Ayesha brought up the subject of adopting children and Karen got scared. Karen opened up to Ayesha about how she previously had a son that she gave up for adoption, shocking Ayesha. Ayesha tried to convince Karen to get custody for her son, but Karen effectively ended the marriage, stating that she didn't want children and never would and if it was a dealbreaker then it was a dealbreaker. Karen and Ayesha's divorce was finalized not long later, and Karen reached adulthood soon after.
Karen was devastated after her divorce with Ayesha, she still loved her very much despite their different interests. After years of trying to forget about her past, she was forced to face up when Blair's spirit rose from the grave outside their home and haunted Karen and the now elder Monique for the night. First Karen fought with Blair and tried to get her to leave, not willing to be tormented by her past. Blair also frightened Monique by in the middle of the night, getting into the bed next to her. Monique, shocked and upset at seeing her dead daughter, ran out of the house screaming and disappeared. Karen searched all over trying to find Monique, and found her asleep, shivering, soaking, and cold on a bench down by the seashore. Monique was already frail with age, but spending the night sleeping out in the rain caused Monique's health to go way downhill.
With Monique's last days approaching, Karen decided to confess everything to Monique as soon as she realised Monique was on her deathbed and had little chance of making it through the night. She confessed the true reason she gave up Dustin, the true identity and fate of Thornton, Dustin's father, and lastly, she confessed to killing Blair. Monique was absolutely destroyed and heartbroken by Karen's revelation, and while she could forgive Thornton's death, she can't forgive Blair's. Karen tried to convince Monique to believe her that it was a mistake, but ultimately Monique sent Karen out of the room. Expecting Monique to have died in her sleep overnight due to her condition, Karen was shocked to wake up and find Monique out of her bed and enjoying the newspaper outside their house. Monique revealed that she's feeling much better and should make a full recovery, and once she does, she's going to report Karen to the police for the murders of Blair and Thornton. Karen, in a moment of frenzy, pushed Monique into the pool. Frail, old, and still not fully recovered, Monique drowned. Karen was distraught it came to this, wanting the cycle of death to end with Thornton. Karen played the part of the traumatized daughter, calling the police and making it seem like a suicide, she claimed that Monique was so upset over her condition she wanted it to end as quickly as possible and be with Blair.
Karen was angered to no end when she found out that in Monique's will, she had originally left the fortune and house to Blair, proving once and for all that Blair was the favourite Stradenflugen daughter. Since Blair was dead, Karen got the fortune anyway. With nothing and no one except her house, money, and cat Jezebel. Karen began to realise she needed to get used to living as a rich but lonely woman, with a whole lot of skeletons in her closet.
Twenty three years after Blair's death, twenty years after Thornton's, and two years after Monique's, the law enforcement of Sunset Valley has decided to re-open all unsolved cases, which include's Blair's and Thornton's (not Monique as she was considered a suicide). With Karen being present at Blair's death, she was interviewed first. Karen kept her original statement, that there was a burglar who attacked them both and Blair was killed in the process. Karen began getting friendly with one of the people involved in the case, new recruit Inspector Vasquez. After the pair went out for a drink, the penny dropped for Karen as she realised that Inspector Vasquez was in fact Dustin, the son she gave up twenty years prior. Karen tried to avoid Dustin, but later came face to face with his adopted parents who recognised her as the birth mother. As Thornton's body was inspected further, they managed to find DNA that was initially missed, DNA matching Karen's. Dustin confronted Karen about the DNA match found on Thornton, which Karen explained by confessing she and Thornton had WooHooed prior to his death.
Dustin became suspicious after a while, and further grilled Karen about the details of their hookup. Karen started to become upset at recalling these events, and Dustin accused Karen of killing him as it's become clear she was the last person he had contact with. Karen blurted out that she and Thornton are Dustin's biological parents, shocking him. Dustin began to put the pieces together and forced Karen to admit that she had killed Thornton after their encounter, Karen explained that he kept her locked up in the bathroom and the trauma was what caused her to kill him and give Dustin up for adoption. Dustin took advantage of Karen's confession, and asked her if she was responsible for the deaths of Blair and Monique, and Karen admitted the truth in an emotional showdown. Karen tried to convince Dustin she wasn't an evil person, and that she killed Blair accidentally and the other two murders were a domino effect from that incident (which was true to an extent). But Dustin had no choice but to arrest her. Karen apologised for the pain she had caused him by abandoning him, before she knocked him out and ran off. Karen realised she had no option but to flee as Dustin managed to voice his suspicions to his superiors before being knocked out, and Karen was officially wanted for the murders.
Karen contacted Ayesha, her ex-wife, and asked her to help her escape Sunset Valley. Ayesha did so only because she still loved her, and had no idea yet that Karen had just been confirmed a murderer. Ayesha helped Karen wrecked the house and left Karen's blood and hair around to make it look like she had been killed, with a little bit of Dustin's DNA left around too to make it seem as though he had killed Karen after the revelation that she was his mother. Karen said goodbye to Ayesha, and after altering her appearance, left for good. Karen also left behind a will, a will that left everything, including the house and money, to Ayesha. Karen also left a letter to Ayesha, apologising for the way their marriage broke up and stating Ayesha was and will always be her true love and as an apology she left Ayesha everything. In the letter, Karen also left Ayesha an adoption agency number, stating that she should use the number to adopt a baby and raise the family she wanted with Karen, but on her own. Karen's current whereabouts are unknown, not even Ayesha is aware of Karen's new name, appearance, or location. Dustin was arrested for Karen's murder, and found guilty as Ayesha testified as a witness. Dustin currently resides in jail, cursing his mother for what she's caused.
- Karen and Blair's relationship was similar to the Pleasant twins Angela and Lilith. One popular sister (Karen/Angela), one goth sister (Blair/Lilith), and they both despise each other. The only difference is the roles are reversed. While with the Pleasant sisters the popular sister is the favorite good sister and the goth child is the overlooked bad sister, with the Stradenflugen sisters the goth one is the favorite and the popular sister is the overlooked one.
- So far Karen has killed three people. She killed Blair Stradenflugen in a sibling rivalry attack gone wrong, she killed Thornton Wolff after he locked her up and attacked her, and she killed Monique Stradenflugen in order to keep her secret from getting out.
- Karen loves her mother very much and despite feeling as though Blair was the favorite child, it is shown Monique also loves Karen (almost) just as much, which explains why Monique simply took Karen's word for the circumstances surrounding Blair's death.
- Karen feels remorse for killing Blair and the effect it had on Monique, but no remorse for the way she initially treated Blair.
- Karen's body count of three murder victims (Blair, Thornton, Monique) officially classes her as serial killer.
- She is similar to another fanon serial killer, Samara Bain. Samara and Karen are very similar both blonde, attractive, and mostly targeted females. But different in other ways such as method of murder, Samara preferred fire, Karen preferred using her fists.
- Surprisingly Karen framing her own son for her murder came easy to her, as while others would think Karen still had some maternal instinct over Dustin despite giving him up, she really viewed Dustin as "just another cop" that she needed to knock down.