One common theme is family. It often explores the relationship between Jeff and his sister in the context of his transformation into a killer. Another theme could be protection, like how the sister might try to protect Jeff or vice versa. Also, there's the theme of horror and how she copes with the terrifying world Jeff has become a part of.
Yes, there are some interesting ones. You can find them on various fanfiction websites. Just search for 'Jeff the Killer Little Sister fanfiction' and you'll get a list. Some might focus on the relationship between Jeff and his little sister, while others could create unique storylines around her character.
Often, there are the victims or potential victims of Jeff. They might be ordinary people in the neighborhood who start to notice strange things going on and suspect Jeff. Another common character could be a detective or a police officer who is trying to solve the mystery of the killings and might eventually cross paths with the little sister.
Well, a plotline might involve the little sister being in a constant struggle between her loyalty to Jeff and her own sense of right and wrong. She might also be hunted by the same people who are after Jeff, which would add a lot of tension to the story. And she could form an unlikely alliance with someone who initially wants to kill Jeff but then realizes she can be a force for good in the situation.
A lot of the fanfiction focuses on the power struggle. Jeff has his own dark power, and sometimes his sister also has some sort of power, and there is a struggle between them in terms of who is more powerful and how that power is used. Also, the theme of protection is there. The sister may try to protect others from Jeff or protect Jeff from himself.
The main characters are Jeff the Killer and the little girl. Jeff, with his terrifying nature, and the little girl, who might be portrayed as either very brave or very naive. There could also be side characters such as the neighbors of the little girl who start to notice strange things happening around her since Jeff entered her life.
Well, regular Jeff the Killer fanfiction might focus on his horror - related aspects, like his killings, his appearance, and his overall menacing presence. But 'lemon' fanfiction, which is not appropriate to go into details, usually involves romantic or sexual elements that are not in line with the typical horror nature of the character. So, the main difference is the inappropriate addition of such elements in 'lemon' fanfiction.
A rather unique 'Jeff the Killer Baby Sister' fanfiction I've read is about her being in a parallel world where Jeff never became a killer. She experiences a completely different life with her brother, but then things start to change when elements from their real world start to seep into this parallel world. It's a long and detailed fanfiction that really dives deep into their relationship.
Killer Jeff was a modern horror urban legend character from the United States. There were also derivative works such as movies and games. According to different versions of the story, Killer Jeff was a serial killer who had lost his mind. He was a villain protagonist who had the urge to kill to satisfy his urge to kill. He had a smile carved on his face with a knife. He would sneak into the target's house at night and order the victim to go to bed. If the victim did not listen to his orders, he would use a knife to kill the target. There were many different versions and stories about the origin and background of Jeff the Killer. In some versions, Jeff was an ordinary teenager who became violent because he was bullied and eventually became a serial killer. In the game, players needed to find skulls in the dark maze while avoiding the killer Jeff. In general, Killer Jeff was a character full of horror elements and was very popular among horror culture lovers.
No, it's not really popular. Popular fanfiction usually involves more common or widely appealing themes. The idea of 'Jeff the Killer' in a 'mpreg' situation is quite outlandish and not something that would appeal to a large number of people. Most people into 'Jeff the Killer' are interested in his horror - related aspects, not male pregnancy scenarios. And those interested in 'mpreg' might be more into other types of characters or settings rather than a horror - based character like Jeff.