The theme of identity is quite common. When Naruto is associated with beasts, he may question who he is now. Is he still the same Naruto? Also, the theme of conflict is often there. There could be conflicts between him and the beasts, or between those who fear his new beast - like form and those who support him. And a theme that ties in with the Naruto series in general is the theme of perseverance. No matter how difficult the situation with the beasts is, Naruto keeps trying to overcome it and do what's right.
One common theme is power. Naruto often gains some sort of beast - related power and has to learn to control it. Another theme is the idea of the other. Since he's dealing with beasts, there's a sense of the unknown and different. Also, friendship is a big theme. Even with his new beast - like qualities, Naruto still depends on his friends. For example, in some fics, his friends help him understand and manage his new powers.
Well, transformation is a very common theme. Naruto might transform into a beast or have some beast - like features. This transformation usually brings about a change in his status and how others view him. Another theme is the exploration of a new world or aspect of the Naruto world. If there's a beast kingdom or something similar, Naruto gets to explore this new area and its rules. And of course, the theme of growth. As he deals with his beast - related situations, he grows as a character both in power and in his understanding of the world.
A frequent theme is the exploration of the beast world. Fanfictions might describe unique landscapes or cultures within the beast world. Also, the idea of Naruto taming or befriending beasts is very common. It gives a new aspect to his character growth. There can also be themes about protecting the beasts from those who want to harm them.
The theme of acceptance is also prevalent. Naruto comes from a world where people with different abilities and appearances are accepted (to some extent). In the 'Naruto and Beauty and the Beast' fanfictions, he might help the characters in the Beauty and the Beast world to accept themselves or others more fully. For example, he could encourage the 'Beast' to accept his cursed form while also striving to break the curse, just as Naruto accepted his own status as a jinchuriki and worked towards using that power for good.
One common theme is the bond between the beasts and the ninja. In Naruto, the tailed beasts are powerful entities, and fanfictions often explore how ninjas interact with them on a deeper level, like forming unbreakable friendships or alliances.
A common theme is the struggle between Beast Boy's humanity and his vampiric instincts. Since he's a beast at heart already, the addition of vampirism can create a complex internal conflict.
Love and romance also feature prominently. There could be stories of secret relationships between members of the two groups, or a member falling in love with a fan who is also a huge supporter of both 4minute and Beast. This adds an element of drama and excitement to the fanfiction.
One common theme is adventure. Fans often write about characters going on exciting journeys to find and tame the beasts. Another theme is friendship. The relationships between the characters and how they bond while on their quests are often explored.
Love is a very common theme. It's about how Belle and the Beast fall in love and how their love overcomes the curse. Another theme is transformation. Not just the Beast's physical transformation but also the emotional and mental transformation of both characters. Redemption is also there, as the Beast tries to atone for his past mistakes.
In Beast World fanfiction, the theme of power is often present. Characters may gain special powers or have to deal with those who have power in the beast world. Another common theme is the search for home. Many characters are displaced and are constantly seeking a place where they belong in this strange new world. There's also the theme of nature and how it functions in the beast world. Some stories explore how the different beasts interact with their natural environment and how the characters must learn to respect and work with it.
Another theme is the power of kindness. Bell's kind nature is what initially draws the Beast to her and also helps her navigate the strange world of the Beast. It's often shown how her kindness can change the attitudes of the other inhabitants of the castle too. In many fanfictions, the contrast between Bell's soft heart and the Beast's initially rough exterior is explored in great detail, highlighting how their differences can actually bring them closer together. This can involve scenes where Bell's small acts of kindness, like helping a little animal in the castle grounds, have a big impact on the Beast and his view of the world.
One common theme is the struggle with identity. Since she's the daughter of a tailed beast, she might not be fully accepted by humans or even by the tailed beasts themselves at first. Another theme could be power. She may inherit great power from her tailed beast parent and have to learn to control it. Also, there could be themes of friendship. For example, she might form unique bonds with Naruto and his friends as they understand her situation.