Summary: What if James wasn't the only Marauder to have a child? Sirius Black had a little girl, who grew up to be everyone's favorite vampire slayer. Buffy learns of her heritage and goes to the wizarding world, to start a whole new life.

Spoilers: Everything up to Order of the Phoenix in Harry Potter and to the end of Season 2 in Buffy. I'm ignoring Half-Blood Prince and all the information in it.

A/N: Ok, so there is going to be a major change in OotP. Sirius did not die. I repeat, Sirius did not die. Although, I respect JK and everything she does, I need him in my story as Buffy's father. Everything else is the same. Harry still went after Bellatrix and met Voldemort and he still learned the prophecy.

A/N 2: This is the last change, I promise. After Becoming, Buffy did not run away to LA. She stayed in Sunnydale and is currently living with Giles. I think that's it. Now, on with the story

Prologue

1977

"We are through with Hogwarts!" Eighteen year old James Potter shouted. James, his best friends Sirius Black, Remus Lupin, and Peter Pettigrew, as well as his girlfriend Lily Evans, had just finished their seven year schooling at Hogwarts School of Witchcraft and Wizardry. Of course, such a momentous occasion required a celebration (according to James and Sirius), so the four of them were currently occupying a booth at the Three Broomsticks, rejoicing in their new found freedom. It was only the four of them as Peter had gone to visit his sick mother, again.

"I know," Sirius exclaimed, "No more homework,"

"Or McGonagall," James continued.

"Or slimy Slytherins,"

"Especially Snivellus,"

"We are finally free!" Sirius finished excitedly.

"You're not going to miss anything at all?" Lily asked.

"Well," Sirius said thoughtfully, "I suppose I'll miss all the girls." Out of the four boys, Sirius was the biggest player.

"Oh really Sirius, you're terrible," Lily said.

"And yet you love me anyway," Sirius said coyly, batting his eyelashes dramatically.

"Merlin knows why," Lily muttered under her breath. Although the two of them argued constantly, they cared about each other very much. Sirius always joked that it was a good thing Lily was dating his best mate because no one else was good enough for his "little sister." Lily would then point out that she was three months older and the two of them would be arguing again.

"Uh-oh James," Remus said teasingly, joining the conversation for the first time, "Looks like Padfoot's after your girl." Padfoot was Sirius's nickname. Sirius, along with James and Peter had become animagi during their 5th year at Hogwarts. An animagus is a person who has the ability to turn into an animal at will. The nickname Padfoot came from Sirius's animagus form. Sirius could turn into a big, black dog. James, or Prongs, could turn into a stag, and Peter, or Wormtail, could turn into a rat. The three of them had gone through three years of training before they were able to achieve this advanced branch of magic. They had done this in order to help the fourth Marauder, Remus, through his transformations. Remus was a werewolf, and while he was a threat to humans, the animal forms of the remaining three Marauders' were relatively safe when Remus transformed.

"You stay away from my Lily, Sirius," James exclaimed, mock angrily.

"You can have her James. I enjoy being a free man," Sirius responded.

"Yea James," Remus said, "You know that Sirius goes through at least six girls a month."

"And I enjoy every minute of it," Sirius retorted.

"Well as fascinating as this conversation is," Lily said sarcastically. "I think we should have a toast."

"About me and my girlfriends?" Sirius asked innocently.

"No," Lily responded, shooting him a glare, "To friendship."

"And new opportunities," James said.

"And happiness," Remus added.

"And peace," Sirius finished.

"Definitely peace," Lily said. They were speaking of the war against Voldemort, the war that was getting worse every day.

"Well, that got depressing," James said, trying to lighten the mood. "Come on guys, we're finished with Hogwarts. Padfoot and I are starting the Auror program. Moony's starting his training to be the best Defense against the Dark Arts teacher ever. Lily's going to become an amazing Unspeakable and Peter's going to work as an assistant at the Ministry. This is the beginning of our lives."

"I know," Lily said. "Everything's changing."

No one knew how true those words were. They couldn't know that just two years from now two of the Marauders would have children. And they couldn't know two years after that, one of the Marauders would be dead, one would be a traitor, one would suffer twelve years in Azkaban, and the fourth would isolate himself from the world to deal with his grief. And the children? One would grow up hated by his relatives, never knowing he was a wizard, and the other, would grow up never knowing she was an adopted witch.

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Ok, so that ends the first chapter. I know it was short but that was just the prologue. Most of it was background information, but I felt like it needed to be there. Next chapter will be the births of Buffy and Harry, and I think I'm going to have Lily and James die in that chapter, also. I want the third chapter to be present day with Buffy and Harry as teenagers.

Please review and tell me what you think. This is my first real story and I'm nervous about how it's going. Thanks!