One great pairing could be Celty and Uta. Celty is a headless rider with a lot of mystery around her, and Uta is a ghoul with a deep love for art and his own brand of mystery. They could share their knowledge of the underground and the strange things they've seen. Another interesting pair would be Shizuo and Ayato. Shizuo's strength and short - temper against Ayato's rebellious and somewhat violent ghoul nature would lead to some intense confrontations. And finally, Izaya and Nishiki could be paired. Izaya loves to play with people's minds, and Nishiki has his own complex relationship with his ghoul identity and his past actions. Izaya could really mess with Nishiki's head in the crossover.
Touka Kirishima and Dean Winchester would be a great pairing. Touka is strong - willed and a skilled fighter as a ghoul, and Dean is a tough hunter. They could have some great banter and action scenes together. Maybe Touka could teach Dean some of her fighting techniques in close - quarters combat, and Dean could show Touka how to use some of his hunting tools.
Kaneki and Zero could make an interesting pairing. Kaneki has his inner turmoil with his ghoul side, and Zero has his own battle against his vampire nature. They could bond over their struggles to control their 'dark' sides and their determination to protect the ones they care about.
Another good pairing could be Jacob and Thor. Jacob's shape - shifting ability and his connection to nature could be something that Thor respects. They could bond over their physical strength and their loyalty to their respective groups. And Thor could introduce Jacob to the world of Asgardian magic and technology.
Another good pairing could be Spartan Locke and Black Widow. Locke is a skilled and stealthy Spartan, and Black Widow is a master spy. They could work together on covert missions, sharing their skills in combat and infiltration. For example, Locke could provide the muscle and high - tech support while Black Widow uses her espionage skills to gather intelligence.
One plot idea could be that a character from Tokyo Ghoul ends up in Ikebukuro (the setting of Durarara). For example, Kaneki could find himself in the middle of the Dollars' activities. He might initially be confused by the different kind of chaos compared to the ghoul world. Another idea is that Celty's head mystery somehow gets intertwined with the ghouls' existence. Maybe there's a ghoul who has knowledge about her head, and this leads to an alliance between Celty and some of the Tokyo Ghoul characters to find out the truth. A third plot could involve the gangs in Durarara getting involved with the ghoul - human conflict in Tokyo Ghoul. They might try to take advantage of the situation for their own gains, but end up getting more than they bargained for as they learn about the true nature of ghouls.
A rather unexpected but potentially great pairing could be Ashley Williams and Vala Mal Doran. Ashley is a tough and no - nonsense soldier in Mass Effect, and Vala is a wily and resourceful adventurer in Stargate. They could get into all sorts of scrapes together and use their different skills to get out of them. On the other hand, Kaidan Alenko and Jonas Quinn could be paired. Kaidan has biotic powers in Mass Effect, and Jonas has his own unique abilities in Stargate. They could explore how their powers might interact or complement each other in different situations.
Happy from Fairy Tail and Jigglypuff would be an interesting pairing. Happy loves fish and Jigglypuff loves to sing. They could have a comical relationship where Jigglypuff's singing puts everyone to sleep except Happy, who just enjoys the performance. And in times of trouble, Happy could fly Jigglypuff around to safety or to strategic positions in a fight.
Iron Man and Ethan Hunt would be an amazing pairing. Iron Man with his high - tech suit and Hunt with his resourcefulness. They could share their knowledge of gadgets and come up with some really cool strategies to defeat the enemy. Another great pairing could be Black Widow and Ilsa Faust. Both are strong female characters with great combat skills and espionage experience. They could work together undercover and take down the bad guys from the inside.
A great pairing would be Cisco Ramon from Arrowverse and Willy Wonka. Cisco is a tech - genius, and he could help Wonka upgrade his factory's technology. They could create some really cool, high - tech candies together. Also, Supergirl and the Candy Man from Willy Wonka's world could be an unexpected but cool pairing. Supergirl's strength and kindness could be used to help the Candy Man, who might be in some trouble, and in return, the Candy Man could offer her some of his amazing candies.
I think Iron Man and C - 3PO would make a great pairing. Iron Man could upgrade C - 3PO's systems, and C - 3PO could provide Iron Man with valuable information about different cultures and languages in the Star Wars universe. They're both tech - savvy characters, and their interactions would be full of witty banter.