Perhaps it's his best friend who has some juicy gossip to share. But it's really bad timing as he's in class. His friend might not be aware of his class schedule.
There's also a chance that it could be a new superhero or villain. Maybe a new hero wants to team up with Spider - Man or a villain is taunting him, starting a new plot in the fanfiction world. This would create an exciting situation for Peter to deal with while trying not to blow his cover in class.
Well, he might get in trouble with the teacher. Teachers usually don't like students getting phone calls during class. So, the teacher could take his phone away and give him a detention.
Well, it depends on who's calling. If it's Tony Stark, for example, Peter would be super excited and might not be able to hide it. He could try to come up with some lame excuse to leave the class, like saying he has a stomachache. But the teacher might not believe him. And his classmates would be curious about who's on the other end of the call.
Maybe it's a family member. For example, his sister could be calling because she needs his help with something urgent at home.
There's also a possibility that it's Trish. She could be calling to warn Dante about a new threat that she has discovered. Dante would trust her information and start to make preparations to face this new danger.
He could be using his phone to track a villain's movements. Maybe he installed some special app on his phone that can detect unusual energy signatures. So while the teacher is droning on about history or math, Peter is secretly following the path of a super - villain who is on the loose in the city.
It could be his friends from his secret group. They might be in some kind of trouble and need his help right away.
His best friend could be a main character. This friend might be the one who rushes to Peter's side when he starts bleeding and tries to comfort him.
Perhaps they call Peter in class because they've discovered some sort of conspiracy that involves the school or someone in it. Peter, being a friendly neighborhood Spider - Man, has a good sense of what's normal and what's not in his neighborhood which includes the school. They might need his help to investigate something strange going on within the school walls.
Any fan who loves the character Peter and has an interest in chibi characters could write it. It could be a young writer who is just starting out and wants to explore the concept of a character getting a cute, little companion.