Goku from Dragon Ball would be a great choice. His quest for power and his experience with intense training could make for an interesting story in the Room of Spirit and Time.
A wise old mentor figure could be interesting. This character could be human and have a lot of knowledge about the world that they can pass on to the non - human protagonist. For example, a retired professor who has studied anthropology and can help the non - human understand human cultures.
A group of thieves could also be included. They might initially try to steal from the Prince of Darkness but end up getting caught in his web of power and secrets. Their street - smart skills and lack of scruples could create some interesting dynamics as they interact with the Prince and other more noble characters.
A powerful Raikage - like character as an OC would be great. This character could be extremely strong in physical combat and have a no - nonsense attitude towards protecting Kumogakure.
The nosy neighbor can be an interesting addition. They might have their own opinions on whether the couple should love their home or list it. Maybe they're jealous and want the couple to move, or they could be overly attached to the neighborhood and try to convince them to stay.
Well, if it's a crossover with Ultraman, Ultraman could be a great addition. His super strength and light - based powers would contrast well with the Jetman's abilities. They could have a friendly rivalry at first but then team up to face a powerful kaiju that is threatening both their worlds.
Definitely Obito. Since they have a long - standing connection, it would be interesting to see how their relationship played out during Kakashi's Anbu days. Maybe Obito was still alive and had his own secret missions within the Anbu that intersected with Kakashi's.
There could be a powerful wizard from a far - off land. This wizard has knowledge of ancient magic that could help or hinder the Son of Neptune. Also, a group of dwarven - like creatures who are excellent craftsmen. They could create special weapons or tools for the Son of Neptune's journey. Additionally, an exiled god who sees the Son of Neptune as a means to regain his former glory.
In a crossover with 'The Last of Us', Joel and Ellie would be great additions. Joel's survival skills and Ellie's immunity could bring new dynamics to the State of Decay world. Also, from 'Left 4 Dead', the four survivors like Bill, Francis, Zoey, and Louis could be included. Their combat skills against zombies could be interesting when combined with the State of Decay gameplay.
Alfred Pennyworth could be included. He could offer his wisdom and support to both heroes. Maybe he even has some insights about the similarities and differences between Gotham and Starling City. Another character could be Felicity Smoak. She could help with the tech - related aspects of the case they are working on together.
A young, aspiring hero who is determined to defeat the Lord of Darkness. This hero could have some special powers or skills that make him a worthy adversary.