I'm not sure specifically as I haven't read this particular fanfiction. It could potentially be about Ratchet and an original character (oc) being put in a cage during lockdown, perhaps exploring themes of confinement, their relationship, or how they deal with this unexpected situation.
I'm not entirely sure specifically what 'ratchet oc omarashi fanfiction' is about as it could be a very niche or specific creation within a particular fan community. It might involve original characters (OCs) in a rather unique or 'ratchet' (which could imply edgy or non - conformist) scenario related to omarashi, but without more context it's hard to say exactly.
There's also 'The Unlikely Bond'. In this fanfiction, the OC is from a different planet and initially has a hard time fitting in with Ratchet's world. But as the story progresses, they form a strong bond. It shows their interactions in different situations really well.
You could write an OC fanfiction where the OC is a young Lombax, similar to Ratchet, but with a different set of skills. For example, instead of being great with guns, they're excellent at stealth and infiltration. They could be on a mission to find out more about their Lombax heritage and end up crossing paths with Ratchet and Clank. Or, an OC who is an alien scientist that discovers a new type of technology that could either save or destroy the galaxy, and Ratchet and Clank have to decide what to do with it.
I'm afraid I can't recommend any 'ratchet oc omarashi fanfiction' as I don't have access to such a specialized body of work. You could try searching in relevant fan communities or specialized fanfiction websites, but be aware that it might be a very specific and hard - to - find type of fanfiction.
A common theme is the relationship between the OC and Ratchet evolving from a simple acquaintance to a deep emotional bond. Another is the OC helping Ratchet deal with the stress of the war against the Decepticons.
You need to understand the Ratchet universe. Know the other characters, the technology, and the overall feel of the world. For example, if there are certain rules about how things work in Ratchet's world, make sure your OC and the story follow those. Also, focus on the relationship development between Ratchet and your OC. It could start as a friendship and grow into something more.
One common theme is empowerment. Writers often depict the female Ratchet as a strong, capable character who can take on any challenge in the universe. She might be shown to be even more resourceful than her male counterpart in some stories.
Well, 'The Unlikely Pairing' is an interesting 'Transformers Prime Ratchet x OC' fanfic. It shows the OC being a mechanic who helps Ratchet in the repair bay and how their relationship evolves from professional respect to something more. There are also some fanfics on platforms like Archive of Our Own. You can search there using the tags 'Transformers Prime', 'Ratchet' and 'OC' to find more hidden gems.