The other characters' reactions would be quite diverse. For instance, the reindeer Sven might sense that something was wrong with Kristoff's mood due to Elsa's kidnapping and nudge him in the right direction during the search. Some of the minor characters in Arendelle, like the townspeople, might be in a state of panic, fearing that Pitch would come for them next if he could kidnap Elsa so easily. Meanwhile, any magical creatures in Elsa's ice palace, like the little snowgies, could start acting erratically, as if they knew their creator was in trouble. And the water spirit Nokk, if it had a connection to Elsa, might try to find her by following any traces of her magic that Pitch left behind during the kidnapping.
Well, Anna would be frantic. She'd immediately set out to find Elsa, not caring about the danger. She might even team up with the Guardians without hesitation. Kristoff would be right by Anna's side, using his survival skills to try and track down Pitch's location. Olaf, being the innocent and loving character he is, would be heartbroken. He might try to cheer Elsa up from afar by singing or reminiscing about their good times, hoping it reached her somehow. The trolls, if they found out, would offer their wisdom and perhaps some magical aid to help in the rescue of Elsa from Pitch's clutches.
The villagers would be in an uproar. Naruto is a hero to them, and the idea of him kidnapping Hinata would be shocking. Some might immediately assume the worst and call for his capture. However, those who know Naruto better, like Iruka - sensei, would try to understand the situation first. They would look for reasons behind Naruto's actions and try to find a way to resolve the issue without causing too much harm. Konohamaru, who looks up to Naruto, would be deeply confused and conflicted. He would want to believe that Naruto has a good reason, but at the same time, he would know that kidnapping is wrong.
Gray would probably be one of the first to want to go after Natsu. He and Natsu have a long - standing rivalry but also a deep friendship. He'd be furious and determined to rescue Natsu. Lucy would be very worried too. She might use her celestial spirit magic to try and find Natsu's location. Erza would be very focused and strategic, rallying the rest of Fairy Tail to come up with a rescue plan.
Sakura would be extremely angry. She's Ino's friend and rival, and she would not tolerate Naruto doing such a thing. She'd probably be the first to go looking for Ino and confront Naruto. Sasuke, on the other hand, might be more calculating. He'd try to figure out Naruto's motives first before taking any action.
Midoriya's friends like Uraraka and Iida would be extremely worried. They would immediately start looking for him. Uraraka might use her quirk to search in the air, while Iida would lead the ground search with his speed. Bakugo, on the other hand, would be furious. He would probably go on a solo mission to find Deku and take on Todoroki without hesitation.
Annabeth would be furious. She'd immediately start planning a rescue mission. She might call on all of Percy's friends and allies at Camp Half - Blood. Annabeth would use her strategic mind to figure out where Nico has taken Percy and how to get him back.
The other Slavic countries would probably be very shocked. Ukraine, for example, might try to mediate between Belarus and Russia. Given their own complex relationships in the Hetalia world, they would want to keep the peace and stability among them.
The other members of Team 7 like Sai would be confused. Sai doesn't fully understand emotions like the others, but he would know that this is a bad situation. He would follow Sasuke and Kakashi's lead in trying to find Naruto and Sakura. Tsunade, as the Hokage, would have to make some tough decisions. She would probably send out search parties while also trying to keep the situation under wraps to prevent panic in the village. The other ninja in Konoha would be on high alert. They would be worried that Naruto's actions could be the start of a larger threat, either from within the village or from outside forces.
One possible plot twist could be that Pitch kidnaps Elsa not for his own gain directly, but to use her as a bargaining chip with the other guardians. For example, he might demand that the guardians give up their powers in exchange for Elsa's safe return. Another twist could be that Elsa discovers a new power within herself while being held captive by Pitch. Maybe her fear and the dark environment somehow unlock a power that is related to shadow or ice in a new way. And a third idea is that Pitch kidnaps Elsa because he realizes that her powers are a key to unlocking a greater power source that he wants to control, but Elsa manages to resist his attempts to use her in that way.
The people of Arendelle would be in a state of chaos and mourning. Elsa has been their queen and their protector. Some might be afraid that without Elsa, the kingdom would be vulnerable to new threats. The trolls, who have known Elsa since she was a child, would also be deeply saddened. They might try to find a way to bring her back, using their own magic and knowledge. Sven, Kristoff's reindeer, would sense the change in Kristoff's mood and would be more subdued, staying close to his owner during this difficult time.
Naruto would be extremely enraged. He would vow to rescue Sakura no matter what. He would immediately start gathering his friends and form a rescue team. Sasuke, on the other hand, might initially seem more reserved but would also be determined to get Sakura back. He would use his Sharingan skills to track Madara.