A really cool Optimus Prime crossover fanfic idea would be with the Gundam universe. The two have similarities in giant mecha concepts. Optimus Prime could find himself in a conflict where the political and military situations in the Gundam world force him to reevaluate his own views on war and peace. Also, a crossover with Star Wars might be interesting. He could interact with the Jedi and Sith, and his concept of the Autobot code could be compared to the Jedi code.
One idea could be an Optimus Prime crossover with the Transformers: Beast Wars. Picture Optimus Prime interacting with the Maximals and Predacons, and how his leadership style might contrast or blend with that of Primal. Another could be a crossover with a superhero universe like the Avengers. Optimus Prime's sense of justice would fit well in that world, and he could team up with Iron Man to share technology or battle strategies.
Well, an Optimus Prime crossover with the Halo universe could be amazing. The high - tech weaponry and complex military strategies in Halo could be a great backdrop for Optimus Prime. He could fight alongside the Spartans against a common enemy. Or, consider a crossover with the Power Rangers. The teamwork aspect is strong in both. Optimus Prime could help the Rangers in a battle against a powerful villain that requires his strength and wisdom.
One idea could be an Optimus Prime crossover with the Transformers: Beast Wars. Imagine Optimus Prime interacting with the Maximals and Predacons, and how his leadership style might contrast or blend with that of Primal. Another could be a crossover with a superhero universe like the Avengers. Optimus Prime could team up with Iron Man, and they could exchange technology and strategies.
One plot idea could be Optimus Prime losing his memory and having to rediscover who he is while the Autobots try to protect him from the Decepticons. Another could be a story where Optimus Prime has to team up with an unlikely ally, like a human who has a special power that can help in the fight against the Decepticons. Or perhaps a plot where Optimus Prime travels to a different dimension and has to find his way back while facing new enemies.
In a different scenario, Voldemort could be in search of a powerful new weapon and discovers a way to control Optimus Prime. Harry and the Order of the Phoenix have to find a way to break the control and convince Optimus to join their side. They could use their combined powers of magic and technology to defeat Voldemort once and for all.
One idea could be a crossover with the Autobots from Transformers Prime and the Titans from Attack on Titan. Imagine the Autobots having to fight the Titans in a post - apocalyptic world. Another idea is a crossover with the Power Rangers. The Rangers and the Autobots could team up to fight a common enemy that threatens both their worlds. A third idea might be a crossover with the Teenage Mutant Ninja Turtles. The Turtles could use their ninja skills along with the Autobots' firepower to take on a new threat in New York City.
One idea could be a story where Optimus Prime has to team up with an unlikely ally from another planet. Maybe a small, scrappy alien that has some unique abilities that can help in the fight against the Decepticons. This would add an interesting dynamic as Optimus has to learn to work with a very different being.
A great plot could involve Arcee getting injured during a fight and Optimus Prime having to protect her while she recovers. During this time, they could have deep conversations about their hopes for the future of their race. Or perhaps there's a fanfic where they discover an ancient artifact that has a connection to both of their pasts, and they have to work together to unlock its secrets.
A plot idea could be that Optimus Prime time - travels. He goes back to the beginning of the war between the Autobots and the Decepticons and tries to prevent it from starting. Along the way, he meets younger versions of his friends and enemies and has to deal with the consequences of changing the past. Or perhaps, Optimus is trapped in a dimension where the laws of physics are different. He has to adapt quickly and find a way back to his own world while also facing off against new threats.
Maybe a plot where Female Optimus Prime teams up with some human female scientists. They work together to develop a new energy source that can end the war with the Decepticons. Along the way, she learns about human emotions and relationships which influence her leadership style.
A plot could revolve around a young fan who writes a lemon - themed story about Optimus Prime. The story somehow comes to life and starts affecting the real Optimus Prime and his world. He has to then find a way to reverse the effects while also learning about the power of human creativity and how it can have unexpected consequences on their reality.
Perhaps a fanfiction where a powerful artifact is discovered that has the potential to change the balance of power on Cybertron. Megatron wants it for his own gain, and Optimus Prime wants to protect it. But when they both touch it simultaneously, they are transported to an alternate dimension where they must work together to find a way back, all while learning more about each other than they ever thought possible.