Godzilla himself could be a central character in a different way. Instead of just being a mindless monster, the fanfiction could give him some sort of sentience or purpose. Maybe he's on a mission to destroy a certain type of Kaiju that is more dangerous than the others. And the Pacific Rim characters have to figure out if they can trust him and work with him towards this goal.
Newt Geiszler could also be a key character. He's the Kaiju expert in the Pacific Rim universe. His fascination with Kaiju could extend to Godzilla. He might try to study Godzilla and figure out how his biology and abilities are different from the regular Kaiju. His insights could be crucial in forming a strategy to fight the common enemies.
Godzilla himself is of course a key character. Focusing on his perspective could be really unique. Maybe we see his thoughts as he encounters the Jaegers and these strange new kaiju. We could explore his instincts and how he decides whether to fight or cooperate with the humans and their giant machines.
One idea could be that Godzilla emerges in the world of Pacific Rim during a Kaiju attack. The Jaegers initially see Godzilla as another threat but then realize he's actually fighting the same enemy. They could team up, with Godzilla's raw power and the Jaegers' advanced technology combining to defeat the Kaiju once and for all.
In this crossover fanfiction, there could be a situation where a powerful Kaiju has some sort of ability that is affecting Godzilla's normal behavior. The Pacific Rim team has to figure out how to reverse this effect while also fighting off other Kaiju threats. They send in their most advanced Jaeger to try and communicate with Godzilla and form an alliance. Along the way, the pilots of the Jaeger learn about Godzilla's history and the ancient battles it has fought against similar threats.
Naruto and Raleigh. Naruto's energetic and fearless nature combined with Raleigh's experience as a Jaeger pilot would make for an exciting pairing. They could learn from each other, with Naruto teaching Raleigh about chakra and Raleigh showing Naruto the ins and outs of piloting a Jaeger.
Wonder Woman could be the most interesting. Her Amazonian training and warrior skills would make her a natural fit in the Jaeger - fighting world. She could also bring her lasso of truth and bracelets to the fight. Maybe she could use the lasso to restrain a Kaiju or figure out some of their secrets. And her strong sense of justice would mesh well with the overall theme of the crossover.
In this crossover fanfiction, the pilots of the Jaegers could be sent to Godzilla's world to learn from his survival skills. Godzilla has been around for a long time and has survived many battles. The pilots observe how Godzilla uses his environment, his strength, and his atomic breath. They then take this knowledge back to their world and use it to upgrade their Jaegers' combat strategies. For example, they might learn new ways to dodge attacks or use the terrain to their advantage like Godzilla does.
Definitely Godzilla and Twilight Sparkle. Godzilla is this huge, powerful force of nature, while Twilight Sparkle is a very intelligent and magically gifted pony. Their encounter would be full of contrasts. Twilight would be trying to figure out Godzilla using her knowledge and magic, and Godzilla would be this unknown entity to her. It would be interesting to see how they interact, with Twilight probably trying to communicate and Godzilla being more of a primal force at first.
First, you need to study both universes thoroughly. Know the characteristics of the Jaegers, their pilots, and the kaiju in Pacific Rim. For Godzilla, understand his powers and his different forms. Then, come up with an interesting concept like a crossover battle or a team - up. Next, create engaging characters, whether they are new or existing ones from the two universes.
One great 'Pacific Rim and Godzilla Fanfiction' is 'When Titans Collide'. It combines the unique elements of both universes really well. The story has amazing fight scenes between the Jaegers and Godzilla. It also delves into how the two different worlds would interact in terms of technology and strategy.
One common theme is the battle between colossal forces. You have Godzilla, a huge and powerful creature, and the Jaegers from Pacific Rim, which are also massive and strong. So, there's often a lot of epic fight scenes.