The theme of friendship and loyalty is also prominent. Ash's existing pokemon friends play important roles. They might help him in battles against threats to the legendary pokemon, or they could be the ones who initially form a bond with the legendary, paving the way for Ash to catch it. For instance, Pikachu might use its electric attacks to protect a legendary from an enemy, and this act of kindness makes the legendary more receptive to Ash.
One common theme is Ash's self - less heroism. He often puts himself at risk to help the legendary pokemon in trouble. For example, when it comes to rescuing a legendary from a natural disaster or from villains.
Another theme is the idea of destiny. It's like the universe has chosen Ash to be the one to catch these powerful beings. In many fanfictions, there are signs or prophecies that lead to Ash encountering and catching the legendary pokemon.
There are also fanfictions where Ash catches Rayquaza. This could be set during a time when the sky is in chaos due to some dark energy. Rayquaza is drawn to Ash because of his pure heart and determination. Ash, with his usual courage, teams up with his pokemon to assist Rayquaza in restoring balance. As a result, Rayquaza allows Ash to catch it.
I think Salamence would be quite challenging. It's a very powerful and aggressive Pokemon. Ash would need to have a really strong team to weaken it first. Also, its flying ability gives it an advantage in battle, making it hard for Ash to land a final blow for the catch.
One common theme is the friendship between Ash and the legendary pokemon. Often, they form a special bond that helps Ash in his adventures. Another theme could be the power of the legendary pokemon and how Ash has to learn to handle it. For example, in some fanfictions, Ash might have to control the immense power of a legendary like Mewtwo without getting overwhelmed.
Protection is also a big theme. Often, Ash has to protect the female legendary Pokemon from villains who want to capture or harm it. This shows Ash's heroic side and also the vulnerability of the legendary Pokemon. In some stories, the female legendary Pokemon also protects Ash in return, highlighting the mutual care between them.
One common theme is the growth of Ash's character. Catching a Legendary Pokemon is no easy feat, and it often forces Ash to step out of his comfort zone, face his fears, and become a more mature trainer. For example, in many fanfics, he has to learn new battle strategies and ways to communicate with a Pokemon that is far more powerful and mysterious than his usual team.
Arceus is quite popular. Given that it's considered the creator of the Pokemon universe in the official lore, it often has a significant role in fanfictions. Mewtwo is also very common. Its powerful psychic abilities and complex backstory make it a favorite for fanfic writers to explore. Another popular one is Lugia. With its majestic appearance and its connection to the sea, it's often a central figure in many stories.
I'm not sure as I don't typically read such fanfictions. But I would assume some common themes could be the exploration of a unique relationship between Ash and the legendary pokemon, perhaps some kind of power dynamic due to the legendary pokemon's abilities.
Well, a great plot might be that Ash enters a special tournament where the grand prize is a chance to catch a Pseudo - Legendary Pokemon. He has to battle tough trainers along the way. Also, it could be that a Pseudo - Legendary Pokemon has some sort of unique ability that Ash discovers he needs to help solve a big problem in the Pokemon world. Maybe it can control a powerful energy source, and Ash must earn its trust to use that power for good.
One popular 'Ash Catches Legendary Pokemon' fanfiction might be 'Ash's Legendary Journey'. In this, Ash could encounter a rare and powerful legendary pokemon early on and through a series of challenges and character growth, he manages to catch it. Another could be 'The Legendary Bond' where Ash forms an unexpected connection with a legendary pokemon that defies the normal trainer - pokemon relationship, leading to its capture. There's also 'Ash and the Legendary Team' which might involve Ash teaming up with other trainers to catch multiple legendaries.
It's the idea of Ash achieving the ultimate status. He's been on a long journey in the Pokemon anime, and the concept of him becoming a Legendary Pokemon Master is like the pinnacle of his growth. Fans love to see how he would handle the power and responsibility.