One way could be that Robin is a lost traveler from another realm who stumbles into Middle - earth. Maybe he has unique skills like archery that could be useful in the battles against Sauron. He could also form an alliance with the Fellowship, sharing his different perspective and knowledge from his own world.
Well, Robin could be a magical being in the fanfiction. For example, he could be a forest spirit similar to the Ents. He might live in the woods of Middle - earth and help the heroes in a more subtle way, like guiding them through the dangerous forests or using his magic to heal the wounded. Since Middle - earth has all kinds of magical creatures, it's not a stretch to imagine Robin in such a role.
In a Lord of the Rings crossover fanfiction, Robin could be a reincarnation of an ancient hero of Middle - earth. He might not remember his past life at first, but as he travels through the land, he starts to have visions and memories. His presence could stir hope among the people, as they believe he is there to fulfill an old prophecy. He could learn the ways of Middle - earth and use his natural courage and determination to fight against the forces of evil.
Robin could be a thief - like character. He could steal important items from the enemy, just like Bilbo stole the One Ring from Gollum. His small size and agility would make him good at sneaking around, and he could provide valuable information to the Fellowship by eavesdropping on the enemy's conversations.
One way could be by having characters from 'Lord of the Rings' appear in the 'Game of Thrones' world. For example, Aragorn could show up as a mysterious ranger in the Seven Kingdoms. He might use his skills to navigate the political intrigue and power struggles, much like he did in Middle - earth.
Begin by exploring the personalities of Robin and the character he is crossing over with. If it's, say, Robin and Supergirl, understand how Robin's detective skills and combat training would interact with Supergirl's superpowers. You can start with a small encounter between them, like they meet by accident and then gradually build up to a bigger adventure. Also, don't forget to add some conflict, whether it's internal (Robin struggling with his own insecurities) or external (facing a powerful enemy).
One way it could work is by having Naruto characters in Middle - earth. For example, Naruto with his shadow clone jutsu could be a great asset in the battles against Sauron's forces. He could create clones to confuse the orcs and trolls. Meanwhile, characters from 'Lord of the Rings' could learn from Naruto's ninja skills. Frodo might pick up some stealth techniques from Naruto's training.
Robin could use his intelligence to analyze Deathstroke's lair and find a weakness in its security system. He might notice a pattern in the guards' patrols or a flaw in the locking mechanisms. Then, he could use his acrobatic skills to create a distraction and slip away unnoticed.
Well, the plot could be about Robin and Spiderman teaming up to fight a common enemy. Maybe a new super - villain has emerged in both Gotham and New York, and their paths cross while trying to stop this baddie. They might start off not trusting each other, but as they see each other's skills and determination, they form an alliance.
One idea could be that Robin, with his detective skills, is investigating a mystery that has ties to the Avengers' world. Maybe it's a series of high - tech thefts that seem to be related to some new villain who has both Gotham - style cunning and super - power ambitions. Robin could team up with Iron Man to analyze the technology used in the thefts. Iron Man would be impressed by Robin's quick thinking and resourcefulness despite not having superpowers.
Batman, of course. He's Robin's mentor and protector. He has the skills, the resources, and the determination to track down Slade and rescue Robin.
Nightwing could also be a likely savior. He was once Robin himself and has a strong bond with the current Robin. He might take it upon himself to rescue Robin, using his own unique fighting style and experience to outwit the Joker. Plus, he has his own network of contacts in Gotham that could help in the search.
Their relationship could grow stronger as they face the challenges of pregnancy together. Franky would become more protective, using his mechanical skills to ensure Robin's comfort. For example, he could build a special chair for her. Robin would rely on Franky more, sharing her fears and hopes for their future family.