One great fanfiction could be about Optimus Prime taking Cade Yeager on a journey through different galaxies to find a new power source for the Autobots. They face various challenges and enemies along the way, and Cade uses his human ingenuity to help Optimus out of tough situations.
A simple fanfiction could be that Cade Yeager discovers a hidden ability within Optimus Prime that no one else knew about. This ability helps them defeat a powerful enemy that was about to destroy the Autobot base on Earth.
One possible plot could be that they team up to fight a common enemy. Maybe a new, powerful Decepticon or Predacon that neither could defeat alone. Their combined strength and different abilities would make for an exciting battle.
At the beginning, they might be cautious around each other. Optimus Prime, being a more traditional Transformer, might find Optimus Primal's more organic and beast - like nature a bit strange. However, as they communicate, they would find common ground in their goals of protecting their people and planets. They could exchange stories about their battles and leadership experiences. For instance, Primal could tell Prime about how he led his Maximals in the Beast Wars, and Prime could share his tales of fighting the Decepticons. This exchange would help them build a bond and understand each other better.
The plot could be really interesting. Maybe Optimus Prime, being from a world of war and machinery, would be a bit out of place in the colorful and magical world of MLP. He might initially be seen as a threat by the ponies, but as they get to know him, they realize he's there to protect. For example, he could help the ponies fight off some new dark force that neither his world nor theirs had faced before, combining his strength and strategic thinking with the ponies' unique magic powers.
One possible fanfiction could be about Sentinel Prime and Optimus Prime having to work together to save Cybertron from a new, powerful enemy. They might start off with some differences in their approaches but gradually learn to combine their strengths.
Optimus Prime could fit in as a powerful ally. He would be like a super - powered being in the RWBY world. His presence could shake up the power balance. Maybe he arrives through a portal and immediately starts helping the RWBY teams fight the Grimm. He could be seen as a symbol of hope, much like the Huntsmen and Huntresses are in RWBY.
Once upon a time, Optimus Prime was resting after a long day of protecting the universe. He parked himself in a quiet corner of the Autobot base. His optics dimmed as he thought about all the battles he had won and the friends he had made. The other Autobots moved quietly around him, knowing he needed his rest. And as he drifted off to sleep, his dreams were filled with visions of a peaceful future for all.
The ponies' reactions would vary greatly. Rarity might be fascinated by Optimus Prime's design and might even try to make some sort of fashionable accessory inspired by him. Applejack would be more practical and would wonder what he was doing in Equestria and if he had any good intentions. Optimus would see the ponies as a new and interesting species. He would be patient with their initial wariness of him and would try to show them that he means no harm. He might also be a bit taken aback by their colorful and somewhat chaotic world compared to the more structured world of the Autobots.
Baby Optimus Prime's character can be developed by exploring his relationships. If he has a mentor figure among the Autobots, his interactions with that character can shape him. He might look up to this mentor and try to imitate their good qualities. His relationship with other baby Transformers or younglings can also be important. He could learn about sharing, cooperation, and friendship through these relationships. Additionally, his discovery of his own strength, both physical and mental, can be a key part of his development. For instance, when he first realizes he can lift a small object that others thought was too heavy for him, it gives him confidence.