It could also be that they are used to Stiles being the one who takes care of them and remembers things for them. He's always been the planner and the one to keep things in order. So they unconsciously assume that he doesn't really care about his own birthday as much as he does about helping them, and they forget all about it.
Well, the plot could be about Percy feeling really sad and left out when everyone forgets his birthday. Maybe he starts to question his friendships. He could go off on his own for a while, and then his friends realize their mistake and try to make it up to him with a big, surprise celebration.
Well, Naruto could initially be shocked that no one remembers. But then he might try to play it cool, because that's his nature. He could also think that they might be planning a surprise later. However, as time passes and still no one remembers, he would start to feel really down. He might even go off on his own to brood about it, wondering if he's not as important to his friends as he thought.
There's a chance it could be Shikamaru. Despite his laid - back attitude, he is quite perceptive. He might notice Naruto's subdued mood and put two and two together, realizing it's his birthday. Then he could rally the others to quickly put together a belated celebration for Naruto.
Obviously, Percy would be the main character. His friends like Annabeth, Grover, and the others from his group would also be important characters. They are the ones who forget his birthday, so they play a big part in the story as they deal with the consequences of their forgetfulness.
A good plot is key too. It could be something that builds on the existing Supergirl storyline in the show, or it could be a completely new and creative take. Like a fanfic where Supergirl and Lena have to team up to save the world from a new kind of threat that only their combined skills can defeat. This makes the story exciting and engaging.
He might be really hurt. Stiles is a sensitive guy deep down, and having his friends, who are like family to him, forget his birthday would sting. He could go into a bit of a sulk and isolate himself for a while.
A common theme is the exploration of their powers and how they interact. For example, how Supergirl's super strength and Lena's intelligence combine to solve problems. Also, there are a lot of 'alternate universe' fanfics. In these, the Supercorp relationship might develop in a completely different setting, like a high - school AU or a fantasy AU.
Love and sacrifice are often seen. The characters might sacrifice their own desires for the well - being of the unborn child. Also, self - discovery is a theme. They learn more about themselves during this special time.
At first, Ginny would be hurt and disappointed. But being Ginny, she'd also be a bit defiant. She might act like it doesn't matter that much in front of Harry, but then go and pour her heart out to Hermione. She'd be thinking about all the times she remembered important things for Harry, and feeling a bit let down. And she might start to distance herself from Harry until he makes it up to her.