Definitely Batman and Circe are essential. But for more depth, you could add characters like Commissioner Gordon. His no - nonsense attitude towards crime - fighting could clash with Circe's more unorthodox methods. Then there's Ra's al Ghul. His long - lived knowledge and connection to the occult could make for an interesting interaction with Circe. And don't forget about Harley Quinn. Her zany personality could bring some humor to a story that might otherwise be quite dark with the presence of Circe's magic.
Commissioner Gordon would also be a good character to include. His relationship with Batman is well - known, and in a fanfic with Owlman, he could be the voice of law and order in Gotham, trying to understand the strange events that are happening with these two vigilantes.
Alfred should be included. He can provide Batman with support and advice, and his unique perspective on things could add an interesting element when Supergirl is around. He might even offer her some tea and wise words.
One idea could be a story where Circe uses her magic to manipulate Batman's mind, making him see illusions of his greatest fears. Another could be a fanfic where they team up against a common enemy, like a powerful sorcerer threatening Gotham. Maybe a story about Circe falling in love with Batman's sense of justice and trying to change her ways.
Alfred would be a great addition. He could offer his wisdom and support to Batman and Batgirl's relationship, and also provide some much - needed comic relief. Another good character is Commissioner Gordon. His connection to the Bat - family and the police force could add an interesting dynamic to the story, especially if he has to deal with the relationship between Batman and Batgirl in some way.
Alfred is a great character to include. He provides wisdom and a sense of family to both Batman and Robin. His insights can add depth to the story.
The Penguin could be a great addition. His wacky and devious schemes always make for an interesting story. Also, Catwoman. Her complex relationship with Batman adds a layer of intrigue. And Oracle, who can provide valuable information and support from afar.
Sonic himself is a must - include. His speed and adventurous spirit drive the story forward. Tails is also great as he can provide technical support and is Sonic's loyal friend. And Dr. Eggman, as the main antagonist, always adds conflict and excitement to the story.
Vegeta is a great choice. His rivalry with Goku adds a lot of drama and action to a fanfic. Also, Piccolo, as he has a long history with Goku and has been both an enemy and a friend. Another good character could be Gohan, Goku's son, as it can explore their father - son relationship further in the fanfic.
Another good character to include is Lex Luthor. He could be the mastermind behind a plot to drive a wedge between Batman and Wonder Woman. His devious mind and resources would make him a formidable antagonist, and his interactions with the two heroes would add a lot of drama to the story.
Optimus Prime is a great choice. His leadership and wisdom can add depth to the story, and his relationship with Bumblebee can be explored further. Also, Sam Witwicky, as he has a strong bond with Bumblebee in the movies. Their friendship can be a central part of the fanfic.