One reason could be that it senses danger nearby. Arcanine has strong instincts. If there is a hidden threat like a sneaky and powerful enemy Pokemon approaching, it might whimper to alert its trainer or just because it's a bit afraid.
Well, it could be that the Arcanine is injured. Maybe it got into a tough battle with a powerful opponent in the fanfiction world and is in pain, thus whimpering.
For a plot, Eevee might be left behind when its trainer goes on an adventure without realizing. Eevee whimpers as it watches the trainer leave. It then decides to go on its own adventure to find the trainer. Along the way, it meets different Pokemon species and has various challenges. It could also be that Eevee is at a Pokemon center where it sees other sick and injured Pokemon. The sight makes it whimper, and it tries to comfort the others. This leads to it making new friends and learning about the importance of kindness in the Pokemon world.
One idea could be '5 Times Bakugou Saved the Day'. It would show his heroic side as he uses his powerful quirk to rescue people in different dangerous situations. Another idea is '5 Moments Bakugou Realized His Mistakes', which would focus on his character growth.
A '5 times bakugou fanfiction' could be really interesting. It might explore five different emotional states of Bakugou. One time could be when he was extremely angry and how that affected his actions. Another time could be when he was vulnerable, perhaps after a difficult battle. Then there could be a time when he was happy and celebrating a victory. And two more times could be related to his growth as a character, like the first time he realized he needed to change his attitude towards his friends, and the second time when he actually made a significant change in his behavior.
Bakugou might react with his usual anger. He could lash out at the bullies verbally or even physically, which might make the situation worse. For example, if someone makes a snide comment, he could respond with a loud and aggressive retort.
Well, Bakugou's development in Bakugou One For All fanfics can be quite complex. Initially, he might struggle with the idea of having a power that wasn't his own. But as the story progresses, he starts to adapt. He becomes more empathetic as he realizes the sacrifices that were made for One For All to be passed down. His relationships with his mentors, like All Might, also change. He becomes more receptive to advice and starts to see the bigger picture of being a hero, not just in terms of strength but also in terms of character and leadership.
Midoriya is very likely to be in it. He and Bakugou have a complex relationship. Midoriya could be the one who either challenges Bakugou to face his fears or is there to support him in the process. Their rivalry - turned - friendship can play a big role in Bakugou's journey of facing his fears.
Bakugou might be initially shocked. He's used to Izuku calling him 'kacchan' for so long that it's become a normal part of their relationship. So, when Izuku stops, it could throw him off balance.
No. It is not appropriate. Fanfic should be a form of creative expression that adheres to ethical and moral standards. Sexual fanfic, especially when related to a character like Bakugou, goes against the respect that should be given to the source material and the character.