They met in 1492, after Katerina (Katherine) was disowned by her family for having a child out of wedlock, and exiled from her home in Bulgaria. She immigrated to England, where she eventually met Elijah and Klaus, who at the time were noblemen. She became friends with them for a short time and Klaus was find to her, in order to manipulate her, but as soon as she found out their intentions with her, she ran away and took the moonstone with her. She then became a vampire after she tricked Rose into feeding her her blood, so she could hang herself and transition. Once Katherine turned, her blood became useless to Klaus, as he needed the blood of a human doppelgänger. As revenge, Klaus found her village in Bulgaria where she was born, and slaughtered her whole family as punishment for thwarting his plans. Katherine then went on the run from Klaus for over five centuries.
In Graduation, Katherine is turned into a human by her doppelgänger Elena, via the Cure. She encounters Klaus in the Mystic Grill and he offers her protection as she is human and has nowhere to go, which leads to Katherine and Klaus having a one-night stand. It is later revealed when they met again in New Orleans that Katherine was pregnant with his child, their daughter Adyelya Mikaelson, who they conceived during their one-night-stand. Their main priority is to protect Adyelya; however, they have disagreements over the best way to protect their daughter.
Throughout The Vampire Diaries Edit
Throughout The Originals Edit
- Katherine was the next doppelgänger after Tatia; a woman whom Klaus was in love with and who was identical to Katherine.
- Klaus eventually develops feelings for Katherine in The Originals.
- Katherine "was taken" with Klaus at first when she had been human.
- Katherine had been the object of Klaus' hatred for over five hundred years after she turned herself to evade his plans.
- In revenge for ruining his plans, Klaus slaughtered Katherine's entire family.
- Katherine ran for over five hundred years from Klaus.
- They both have absentee parents (Katherine was disowned, and Klaus didn't know his biological father).
- Klaus has a special nickname for Katherine; "Little Witch", whereas with other girls, he calls them "love".
- Klaus called her "Little Human" once in The Vampire Diaries.
- He has also referred to Katherine as "witch girl".
- The people who raised them thought of them as disappointments. Katherine's parents disowned her and sent her to England for having a baby out of wedlock, and Mikael tried to kill Klaus because of Esther's affair.
- Klaus has grown feelings for Katherine; however, he will not solidify his relationship with her because he knows that Elijah loves Katherine as well.
- Klaus asked the vampires in Reigning Pain in New Orleans to show respect towards Katherine at the feast.
- Klaus chose to share the discovery of his werewolf clan relatives with Katherine.
- Katherine doesn't believe that Mikael's words of Klaus being an abomination are true.
- Klatherine shared a scene in From a Cradle to a Grave, where Klaus felt the baby kicking.
- Klaus named their daughter Adyelya.
- Klaus and Katherine gave Adyelya to Rebekah to keep her safe. They both had the same opinion about it; they were distraught to do it, but in the end, they wanted what was best for their daughter.
- In Rebirth, Elijah said that Klaus is the only one who can truly understand how Katherine feels.
- Klaus said she was his family in Rebirth.
- In Every Mother's Son, he gets upset that Katherine is thinking about switching bodies.
- In The Map of Moments, they are reunited with their daughter Adyelya after four months apart.
- Katherine is the first person Klaus said the words, "I trust you" to.
- Klaus' nickname for their daughter, littlest witch, stems from the nickname he gave Katherine.
- As of An Old Friend Calls, their originally-decimated relationship and friendship (due to their betrayals to each other) is currently on its way to repair. They decide to run away together in order to keep Adyelya safe and for Klaus to stay alive from the enemies hunting him due to his unlinked sireline.
- In Alone with Everybody, they have a honest and deep talk about what's best for their family and for their daughter and they come to an agreement. They will decide together what's best for Adyelya as partners.
- In Where Nothing Stays Buried, Lucien refers to them as King and Queen.
- Klaus bowed down before Lucien to save Katherine's life.
- It is currently unknown if Katherine and Klaus knew about the deaths of Tyler and Stefan.
- Katherine spent five years of her life tracking down the seven werewolf families whose venom would help her save Klaus and the rest of the Mikaelsons.
- Hayley helped Katherine to do this.