Wonder Woman could be a great addition. She could have a connection to both Batman and Supergirl. Maybe she helps them in a battle or mediates between them when they have different approaches to a problem.
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.
Supergirl is also a great character in fanfic. Writers can play with her powers, her fish - out - of - water experience on Earth, and her relationship with Batman. Her naivete about some Earth things combined with her powerful abilities make for interesting stories.
Well, Cisco Ramon from The Flash would be a great addition. He could use his tech skills to create some new gadgets or figure out ways to counter the villains' powers. Also, Martian Manhunter from Supergirl's side. His shape - shifting and telepathic abilities would add a whole new dimension to the story.
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.
Jimmy Olsen could also be a great character to include. He is Superman's friend and colleague at the Daily Planet. His loyalty and his ability to get into some sticky situations can add a touch of humor and also some interesting sub - plots to the Supergirl and Superman fanfiction.
Definitely, Cisco Ramon from Flash. He can add some tech - savvy humor and his ability to create new gadgets can be really useful in the crossover. For example, he could make a device that helps Supergirl deal with a new type of kryptonite - like threat.
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.
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.
Well, Oracle would be an excellent character to include. She has vast knowledge and can assist Batman with intelligence. Catwoman could also be involved. Her ambiguous relationship with Batman could create some tension, especially in a story with Red Claw. And then there's Nightwing. He has his own skills and experiences that could contribute to the plot. He could be a backup or a co - investigator with Batman in the fight against Red Claw. For example, Nightwing's acrobatic skills might come in handy when infiltrating Red Claw's hideouts.
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.
Obviously, Supergirl herself should be included. Her presence can add more drama and conflict, especially if she has mixed feelings about Lena and Mon - El's relationship. J'onn J'onzz could also be a great addition as he can offer his wisdom and alien perspective.