Ender is definitely one of the most popular. Since he's the main character in the original story, a lot of fanfic focuses on him, maybe giving him new adventures or exploring his emotions further. Another popular character is Valentine. She has a complex relationship with Ender, and fanfic writers like to delve into that more. And Petra is also popular as she was one of Ender's closest friends and comrades in Battle School.
Some Enders Game fanfic explores the concept of time travel within the universe of the story. Imagine if Ender could go back in time and change certain events that led to the war with the Buggers. Another concept is the expansion of the mind - what if the children in Battle School could develop even more extraordinary mental powers? And then there are fanfics that deal with the post - war reconstruction, showing how the humans and the Buggers (if they survived) would rebuild their worlds and relationships.
Ender Wiggin is the most important character. He's a brilliant and complex boy chosen for Battle School to train to fight the Buggers. Valentine, his sister, is also important. She has a deep connection with Ender and represents a more empathetic side. Colonel Graff is a key figure too. He's in charge of Ender's training and often makes difficult decisions regarding Ender.
The main themes include survival. In the harsh environment of Battle School and the threat of the Buggers, characters have to fight to survive. There's also the theme of manipulation. The adults in the story manipulate the children, especially Ender, for their own ends in the war against the Buggers. And the theme of identity. Ender struggles with who he really is as he's shaped by the military training.
One common theme is the exploration of Ender's character further. Writers often want to dig deeper into his psyche, like his guilt and how he copes with it. Another theme is alternate universes. They create different scenarios for Ender, such as if he had made different choices during the battles. Friendship is also a theme, showing his relationships with other characters in new lights.
In 'Enders Game', Mazer Rackham's story is crucial. He was the hero who defeated the Formics in a previous invasion. His victory became a legend and a strategic model. Ender was later trained based on Rackham's experiences.
The theme of leadership is prominent. Ender has to lead in difficult situations, making tough decisions. Also, the idea of identity is there. Ender struggles to define himself as a person outside of the military expectations placed on him.
Ender is the most important character. He is a brilliant child who is chosen for military training. His sister Valentine also plays a significant role. She is a source of kindness and normalcy in Ender's life.
Valentine is also very important. She is Ender's sister. She represents the emotional connection that Ender has to his family and a more empathetic side of humanity. She has a different path from Ender but still plays a role in his life.