Maybe in the fanfiction, Cyborg and Robin find themselves in an alternate dimension where they are the only ones who can save that world from destruction. It could involve them making difficult choices and sacrificing things to succeed.
Another interesting storyline could be that there is a malfunction in Cyborg's systems which causes him to act erratically. Robin has to figure out what's wrong while also dealing with the chaos that Cyborg's malfunction is causing, all while an external threat looms.
Perhaps a story where they accidentally swap powers for a while. This would lead to humorous situations as they try to adapt to each other's abilities while still being themselves. They could also learn a lot about each other during this time.
Cyborg is often depicted as strong, both physically and technologically. He's the one with all the cool gadgets and a bit of a tough - guy exterior, but deep down he has a heart of gold. Robin, on the other hand, is the strategic mastermind. He's intelligent, quick - thinking, and always has a plan. In fanfiction, these traits are usually amplified to create more dramatic situations.
A great storyline might be a crossover where Danny and Robin end up in each other's universes. Danny has to deal with the more crime - filled Gotham while Robin has to handle the ghostly threats in Amity Park. This would lead to a lot of character development as they adapt to new situations.
A really cool storyline could be a time - travel one in the fanfiction. Batman, Robin, and Batgirl are sent to the past or future Gotham. In this new time period, they have to adapt to different versions of the city and its threats. Robin might be especially fascinated by the differences in technology and crime - fighting methods, and together they work to find a way back to their own time.
One interesting storyline could be Robin growing up and struggling to step out of Batman's shadow. He wants to prove himself as an independent hero while still respecting Batman's teachings.
A plot could revolve around Raven getting injured during a battle. Cyborg takes it upon himself to nurse her back to health. As he tends to her, they have long conversations that lead to a deeper understanding of each other. This newfound closeness could then develop into a romantic relationship in the context of the fanfiction.
One interesting storyline could be Chopper discovers a new type of medicine on an island and Robin helps him research it. Their different skills, Chopper's medical knowledge and Robin's ability to read Poneglyphs, combine to unlock the secrets of this new medicine which could potentially save many lives in the One Piece world.
Another possible storyline is a time - travel story. Robin and Megan accidentally get sent back in time. They have to work together to find a way back to their own time while also trying not to disrupt the past too much. Along the way, they learn more about the origins of the Justice League and how their predecessors dealt with threats, which gives them new perspectives on their own roles as heroes.
One interesting storyline could be Robin exploring and mastering new powers that are unique to fanfiction interpretations. For example, he might develop the ability to communicate with animals in a way that's different from his usual skills. This could lead to him forming an animal - based team to help fight crime.
One interesting storyline could be them teaming up to face a powerful new villain that neither of them can defeat alone. They combine Robin's strategic mind and Supergirl's super strength to outwit the enemy.