Archive of Our Own (AO3) is a great place to start. It has a vast collection of fanfictions, including many on the Loki baby daddy theme. You can use the search function and type in relevant keywords to find the stories you're interested in.
One popular Loki baby daddy fanfiction might be the ones where Loki discovers he has a child in the mortal realm. In these stories, there's often a lot of drama as he tries to adjust to being a father while also dealing with his Asgardian duties and his complex personality. For example, some stories focus on how he initially rejects the idea of fatherhood but gradually grows into it as he forms a bond with the baby.
First, do your research on Loki and Sigyn's characters from the original myths. This will help you write them accurately. Then, think about the baby's character traits. Will it be more like Loki or Sigyn? Next, create a plot that is engaging. For example, a quest to protect the baby from an evil force. Also, use vivid descriptions of the settings, whether it's the magical realm of the gods or a more earthly - like place in their world. And don't forget to add some emotional depth, like the love Loki and Sigyn have for each other and for their baby.
Obviously, Danny Phantom himself could be the 'baby daddy'. His dual nature as a human and a ghost could bring a lot of interesting twists to the story of having a baby. For instance, the baby might inherit some of his ghost powers, which would create all kinds of challenges for raising the child.
In Naruto fanfiction, characters like Jiraiya could also be a 'baby daddy'. He was known for his womanizing ways in the series, so it's not hard to fathom a situation where he has a child. Then there's Itachi. Although his life was full of tragedy and secrecy, a fanfiction could explore a scenario where he has a child before his untimely death. And Kiba could be a character as well. His close bond with his dog Akamaru and his brash personality could lead to a situation where he becomes a 'baby daddy' in a creative fanfiction.
One great Loki and Sif baby fanfiction could be about the challenges they face in raising a baby with Loki's mischievous nature and Sif's warrior strength. Maybe the baby inherits some unique powers that they have to figure out how to handle.
You can also check out Tumblr. There are often writers who post snippets or links to their baby Loki fanfiction on their blogs. Additionally, Tumblr communities dedicated to Loki might have discussions and recommendations for such fanfictions.
One popular 'baby daddy Draco' fanfiction might be 'Draco's Unforeseen Fatherhood'. It delves into how Draco discovers he has a child and his journey to become a responsible father. Another could be 'The Secret of Draco's Baby' which might explore the mystery behind the baby and how it changes his relationship with the other characters. There's also 'Draco and His Little One' that could focus on the tender moments between Draco and his baby.
Iruka sensei is another possibility. He is kind and nurturing, having already shown his care for Naruto when he was a student. As a baby daddy, he would be patient and dedicated to raising his child with good values and a love for learning.
One great Loki and Natasha baby fanfiction is 'A New Beginning'. It explores how they handle the challenges of having a baby in a world full of chaos and superpowers. The story is really engaging as it shows their different parenting styles.
One interesting Loki and Jane baby fanfiction could be where Loki discovers he has a paternal side when Jane has their baby. He starts using his magic to create little amusements for the baby, like floating toys. It shows a softer side of Loki that we don't often see in the original stories.