Well, Annabeth would be extremely focused on saving Percy. She'd be racking her brain for any knowledge she has about poisons from her studies. Grover would be nervously pacing around, but also trying to comfort Percy. Leo, if he's around, would start tinkering with some of his inventions, thinking he could come up with a device to detect or neutralize the poison. His friends' reactions are all centered around their love and loyalty for Percy, and they won't stop until they find a way to cure him.
His friends would be very worried. Annabeth would immediately start looking for solutions. She'd be using her strategic mind to figure out what kind of poison it is and how to get an antidote. Grover would be freaking out a bit but still try to be useful, like using his sense of smell to detect any strange scents around Percy that could give a clue about the poison.
Annabeth would probably be very worried and take charge. She'd start researching immediately, looking through books in the camp library to find a cure. Grover would be constantly by Percy's side, using his nature - related powers to try and make Percy more comfortable, like bringing in fresh air and plants to help him feel better.
Timmy's friends' reactions can vary. Cosmo might accidentally make the situation worse by using the wrong spell in his haste to help Timmy. Wanda would be more level - headed and try to correct Cosmo's mistakes. Chester and AJ would be really concerned and would try to comfort Timmy. They might hold his hand or tell him that he'll be okay. In some fanfictions, if Timmy is in a coma or seriously injured, his friends would be constantly by his side, waiting for him to wake up and doing whatever they can to speed up his recovery.
He might be initially in shock. Percy has been through a lot with Annabeth, so being dumped would come as a huge blow. He could be speechless for a while, unable to process what has just happened.
They might be a bit in awe at first. She has a certain presence about her that comes from her being a demigod. Maybe they're curious about her and ask Percy a lot of questions about her later.
If his friends continue to ignore him, Harry could become sad and withdrawn himself. He might start to isolate more, spending time alone in places like the Forbidden Forest or an empty classroom. He might also lose his confidence in himself, thinking that he is not worthy of their friendship. In his loneliness, he could focus more on his studies or some solitary magical pursuits, trying to distract himself from the pain of being ignored.
Well, he might be really flustered. Percy is often portrayed as a bit of a goof in some fanfictions. He could stutter and turn red, not really knowing how to handle the situation.
Hermione would usually be very worried and immediately start looking for ways to heal him. She might use her knowledge of magic to find the right spells or potions to treat his injuries.
Some might be excited. They've probably heard a lot about Percy from Annabeth, so they are eager to meet him in person.
They could be initially shocked. They might not have expected Harry to leave at all. Some friends could be angry, feeling betrayed that he left without proper explanation.
Well, he could experience intense pain and weakness. Depending on the type of poison, it might affect his connection to his father Poseidon. Maybe he'd be unable to communicate with sea creatures or draw strength from the ocean as he usually does. His friends would be in a panic. They'd probably split up, with some staying to take care of Percy while others go on a quest to find the source of the poison and a cure. Chiron at Camp Half - Blood would also be involved, providing what knowledge he has about such poisons.