The Harry Potter books were packed with information about several characters who don't get the same development or screentime in the films. Of those characters, the Marauders, Lily Evans, and Severus Snape are all included. While Snape, Sirius, and Remus all play major roles in Harry's life, especially in the books, the movies do not show as much of their history. If their years in Hogwarts got a spinoff, there would be an opportunity to tell the stories that novels referenced about their childhoods.
Fans had eagerly wanted a Marauders spinoff to see these characters before they grew up. It would be a chance to see what they were like when they were young, happy, and idealistic rather than the hurt people they were by the time Harry met them.
Becoming Animagi
When James, Sirius, and Peter learned that their friend Remus was a werewolf, they didn't leave him. Instead, they chose to find a way to help Remus. By transforming into animagi, they could go with Remus to the Whomping Willow when he transformed.
As animals, they would run around with Remus keeping him occupied and less likely to hurt himself or an innocent person. Such a transformation must have taken time to accomplish. It is an aspect of magic that Harry and his friends never experienced for themselves, meaning that it would be fresh material.
Learning Remus Is A Werewolf
When did the boys learn Remus was a werewolf? He would have disappeared with every full moon, but how long did it take them to figure out the truth? How did they initially react? What did Remus do when he realized his friends knew his secret?
This could have been a secret with the potential to test their friendships. Luckily, Remus was accepted and kept his friends. This storyline could also follow Snape and Lily learning the truth as well.
Original Order Of The Phoenix
The Order of the Phoenix is first introduced during "Harry Potter and the Order of the Phoenix." Harry learns of it during the Order's second time in existence. The first time the group came to be was during Voldemort's initial rise to power.
Voldemort was becoming a threat while the Marauders were at Hogwarts. As Sirius explained that he, Remus, James, Lily, and Peter were all , there was a possibility to include this aspect. It could also be used to expand on Frank and Alice Longbottom.
Snape And Lily
The friendship between Severus Snape and Lily Evans was a major part of Snape's life and motivation. The two had met as children, with Snape being the first to tell Lily she was a witch. As they grew up, their friendship remained intact even with their houses at odds.
Unfortunately, their friendship would come to a horrible end a few years later. Snape called Lily the worst thing a person could call a Muggleborn, which ended their friendship. Lily also did not like that Snape hung out with others interested in Dark Magic, something Snape also practiced.
Sirius Black's Family
Sirius Black came from a home of Pure-Blood supremacy. His parents were harsh, and it was known that of the Black family were traditionally Slytherin. This aspect is briefly mentioned in the films but is not a major part.
The books go into more detail about Sirius Black's home life, brother Regulus, and Sirius being removed from the family tree. Another detail the movies don't heavily reference is how Sirius Black, Narcissa Malfoy, and Bellatrix Lestrange are all related.
Pettigrew The Traitor
The Weasley family had Scabbers as a pet rat for twelve years before Ron learned that his beloved pet was Peter Pettigrew in his animagus form. Peter Pettigrew, also known as Wormtail, had been the fourth Marauder.
He had been best friends with James, Sirius, and Remus during school, and when Sirius determined that he was too obvious a choice for Secret Keeper, he offered that Peter replaces him. Unknown to them at the time, Pettigrew would sell them out to Voldemort. But, how long had Pettigrew been a spy for Voldemort? What caused him to change sides?
James And Lily
Harry mostly learned about his parents from seeing Snape's memories and hearing stories from Sirius and Remus. While James had a huge crush on Lily, Lily did not like James. He was cocky, arrogant, and had a bad habit of constantly picking on Snape.
Their relationship was thought of as very antagonistic for years before James mellowed out, and Lily fell for him too. While not alive throughout the Harry Potter series, James and Lily are major characters who had left a mark on their friends.
Sirius Runs Away
Sirius Black did not have the best home life. When Sirius finally ran away, he was taken in by James and his family. Such an event would have emotional ramifications, and Sirius's name would be removed from the family tree.
Sirius and James's friendship would be strengthened by living together so much, and it would give more understanding of who Sirius Black grew up to be.
Lily And Petunia
Petunia Dursley does not make the best first impression with her awful treatment and attitude toward Harry.
Later on, it was revealed that Petunia was deeply jealous of Lily's magical gift, and that jealousy transformed into anger and bitterness. Petunia looked at her sister as a freak and grew to resent her. However, their story was never shown through Lily's eyes.
The Werewolf Prank
The Marauders were known for their pranks, but on one particular occasion, Sirius went too far. Knowing that Snape was suspicious of what the boys were up to, Sirius told Snape how to get into the Whomping Willow so that Snape would finally know that they were hiding.
Sirius knew that Remus would be a fully transformed werewolf at that point and had been willing to let Snape go anyway. James, eventually realizing what would happen if Snape encountered Remus as a werewolf, rushed after Snape to save his life. Had things gone wrong, it would have ended up with horrible consequences for Sirius, Remus, and Snape.
