The interactions could be full of surprises. For instance, Bellatrix might be enraged by the presence of the Marauders and Sirius in particular. But Narcissa could be more curious. She might see the Marauders as a different kind of wizarding group. And the Marauders would likely be shocked by the coldness and strict hierarchy within the Black family. They would probably try to break down some of those barriers with their humor and camaraderie. There could also be a moment where a young Black, like Regulus, looks up to the Marauders in a way, which would further complicate the family dynamic.
They might interact with suspicion at first. The Black family may be wary of the Marauders' Gryffindor ways and their more liberal views. Sirius would be the link between the two groups. He could try to ease the tension, but it might not be easy. Some of the Marauders like Remus might be more reserved in the interaction, while James and Sirius could be more confrontational if the Black family members start spouting pure - blood nonsense.
In fanfiction, when they meet, there could be a mix of emotions. The Marauders would likely feel a sense of protectiveness towards Sirius when facing his family. The Black family might have a mix of disdain and curiosity. The older members would show disdain for the Marauders' lack of regard for pure - blood traditions. But the younger Blacks could be curious about the Marauders' adventures at Hogwarts. There could be a power struggle of sorts, with the Marauders trying to show the Blacks that their way of thinking is outdated and the Blacks trying to assert their family's long - held beliefs.
They might start off as enemies. Sirius doesn't get along with his family, so he may not want the Marauders to have anything to do with Regulus. But sometimes, they could end up working together for a common good.
In fanfiction, when the Marauders meet the Black family, there could be a lot of drama. Sirius Black might be in an awkward position as he has distanced himself from his family. There could be arguments between the Marauders and the more traditional members of the Black family over things like blood purity. Maybe James Potter would be overly protective of Sirius and say something to Sirius' family members that would stir up more trouble.
They might interact with a great deal of suspicion. The Dursleys would be suspicious of the Grangers because they are Hermione's parents and are associated with the wizarding world that they despise. The Grangers could be suspicious of the Dursleys' behavior towards Harry. So, their initial meeting might be full of cold stares and curt exchanges.
Often, their interaction is full of unspoken words. Felix may have a hidden agenda, while Adrien is just trying to be friendly. They could end up in a sort of power struggle, each trying to assert their own identity. But as the story progresses, they could start to respect each other more and find common ground.
In fanfiction, the Marauders interact with baby Harry in multiple ways. James, being Harry's father, is extremely affectionate. He showers Harry with hugs and kisses. Sirius, on the other hand, is the fun - loving uncle type. He might take Harry on little broom rides around the house (using magic to keep him safe of course). Remus is the gentle storyteller. He shares tales of magical creatures and ancient spells with Harry. And Peter, well, he tries to be helpful in his own way, like getting Harry his favorite toys. Their interactions are full of warmth and a sense of family.
They might interact with a mix of caution and boldness. Harry, out of habit, would be cautious not to upset the Dursleys too much. Ginny, though, could be bold. For example, she might directly ask Vernon why he's so against magic when it can do so many wonderful things. Harry would be in the middle, trying to translate the Muggle - magic misunderstandings between them.
When they meet for the first time in fanfiction, Sonic could be running from Dr. Eggman and accidentally runs into Tails' hiding place. Tails is scared at first, but Sonic quickly reassures him. They start talking, and Sonic is amazed by Tails' intelligence and his ability to build things. Tails is inspired by Sonic's courage and they become friends right away, sharing their goals of stopping Dr. Eggman.
The Marauders would likely have a very negative reaction to the Dursleys. Sirius, having run away from his own awful family, would not tolerate the Dursleys' treatment of Harry. He'd probably confront them right away.
Obviously, the Marauders which include James Potter, Sirius Black, Remus Lupin, and Peter Pettigrew. And then there are the Evans family members. Most likely Lily Evans, who is quite important as she has her own story arc and connection to the Marauders, especially James. There might also be other Evans siblings or family members depending on how the fanfiction is written.
The main characters would be the Marauders, which include James Potter, Sirius Black, Remus Lupin, and Peter Pettigrew. And of course, Tonks is also a main character in this fanfiction.