After he throws up, he might discover a new clue. For example, the vomit could have some strange color or texture that indicates what kind of poison or magic is affecting him. Then he could start looking for a cure.
One of the most dramatic scenes could be when he throws up in the middle of a battle. Imagine he's facing a horde of monsters, and suddenly he starts to feel sick. He's trying to hold it in while fighting, but eventually he can't and it throws off the rhythm of the battle, both for him and his allies. It adds a sense of vulnerability to the usually strong Percy.
Perhaps he has been exposed to some sort of deadly and unknown substance in the mythical world. This could be a new type of monster venom or a strange plant that he accidentally ingested. The substance could be attacking his body from the inside, causing his internal organs to bleed, and thus he throws up blood.
Grover would be panicked. He's Percy's friend and he cares a great deal about him. He might start running around trying to find help, like looking for a healer or someone with magical healing abilities. He'd probably be muttering to himself about how he should have protected Percy better.
Try this one: 'Are you a demigod? Because you've got the power to make my heart race faster than a satyr at a party.' Satyrs in the series are known for their energetic and wild nature, so comparing the effect the person has on your heart to a satyr's energy is a fun way to flirt. It also ties in the concept of demigods which is central to the Percy Jackson world.
Yes, in some Percy Jackson fanfics, he could be depicted as a Titan. Fanfic writers often take creative liberties and might come up with unique storylines where Percy has Titan - like qualities or is even reimagined as a Titan for the sake of an interesting plot twist.
Well, he might start by trying to find a way out. The Isle of the Lost is a place full of villains and their descendants, so Percy would be on high alert. He could use his water powers to his advantage, like finding hidden water sources or using the water to sense danger. Maybe he'd team up with some of the less - evil characters there and try to bring some order to the chaos.
Well, it could be due to some sort of magical potion gone wrong. Maybe he drank something that was supposed to give him extra strength but instead made his stomach turn. Another reason could be that he got poisoned during a battle with a monster. Some monsters might have venom or toxins that could make him sick to his stomach.
Maybe it could be a rogue demigod who is jealous of Percy. This demigod could be working with some dark forces and tries to make Percy's situation worse while he's holding up the sky. They could spread rumors among the demigod community to turn others against Percy, making it harder for his friends to get help.