Another possibility is that Neji is initially shocked and then becomes self - conscious. He might start to wonder if there is something about him that gives off a girlish vibe. This could lead to some internal monologue in the fanfic where Neji is evaluating his appearance, behavior, and how others see him.
He could also play along. Neji might be confident enough in his masculinity to just roll with the joke. He could give a witty comeback like 'Even if I were a girl, I'd still be stronger than you, Naruto.' This shows that he's not easily ruffled by Naruto's comment and can handle it with humor.
Neji might get angry. He's a proud character, and being called a girl in a somewhat derogatory way (if that's how he takes it) could make him lash out at Naruto. He could give Naruto a cold stare and tell him to watch his words.
He might be really hurt. Naruto has always been an outcast and being called a demon again could reopen old wounds. So he could just stand there in shock and disbelief, his eyes wide with pain.
He might be initially shocked. Since he sees himself as a good mentor, hearing such a harsh accusation from Naruto could leave him speechless for a moment.
He could also get angry. After all, being misjudged like that is unfair. His anger could lead him to either lash out verbally at Sakura or he could leave the village in a fit of rage, feeling that he is not accepted even by his friends. This could then lead to a series of events where Naruto has to find his own way and Sakura realizes her mistake later on.
Maybe Naruto is just teasing Neji. In the Naruto world, friends often playfully taunt each other. Naruto might have seen Neji do something that he thought was more like what a girl would do, like being overly cautious or having a particular grace in his movements. It could also be a random joke that Naruto came up with to get a reaction out of Neji.
Naruto could also feel a sense of confusion. He might wonder what he did wrong or what made Fem Kyuubi choose Sasuke over him. This confusion could lead him to question his own worth and his relationships with others. However, in true Naruto fashion, he would eventually rise above these negative feelings and focus on his goals, like protecting the village and his friends.
Naruto might be overjoyed. He's always been someone who values friendship and love, and Hinata's confession could be like a dream come true for him. He could immediately accept her love and start planning a future together.
Peter could also be a bit annoyed if it's not a good time. For example, if he was really focused on a test or a lesson he was interested in. But still, he'd probably answer because he knows Natasha wouldn't call without a good reason. He might give her a look that says 'this better be important' while trying to listen to what she has to say.
Naruto might initially be shocked or confused. For example, if they prank him with the fake ramen, he'd probably make a really funny face when he takes the first bite. But then he'd probably laugh it off because he has a good sense of humor.
He could be touched. Despite his stoic exterior, Itachi may see this as a genuine and innocent gesture from Naruto, and it could warm his heart in some way. Maybe he starts to see Naruto in a new light, as someone who can bring a bit of light - heartedness into his world of shadows.
At first, Jiraiya would be in shock. He couldn't believe that Naruto has become so dark and left him. Then, he would be determined to bring Naruto back. He would follow Naruto's trail, trying to understand his motives. Along the way, he might face some challenges from Dark Naruto's new allies or the places he visits. But Jiraiya would not give up easily, as he truly cares about Naruto and wants to save him from the darkness.