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.
I'm not entirely sure of the exact details as there can be many different interpretations. But generally, 'jeff the killer mpreg fanfiction' is a form of fan - created literature. It might explore things like how Jeff the Killer would react to being in a situation of male pregnancy. It could be full of horror elements as Jeff is a horror character, or it could take a more creative and unexpected turn, perhaps using the mpreg as a way to show a different side of Jeff, like a more vulnerable side that we don't usually associate with his typical menacing self.
The relationship can be portrayed as a terrifying one. Jeff could be seen as a predator and the reader as his prey. He might stalk the reader, leaving little signs of his presence to scare them. For example, he could leave a bloody knife on their doorstep.
Jeff the Killer is purely fictional. It's a made-up tale that has gained popularity in certain online communities, but there's no truth to it. It's all for scaring and thrilling those who enjoy such horror concepts.
Jeff the Killer is purely fictional. It was created and spread through various online platforms and has no basis in real events. People just came up with the creepy tale for entertainment or to scare others.