Another could be an OC with the Omnitrix getting stuck in a parallel universe where the rules of the Omnitrix are different. For example, instead of being able to transform into known aliens, the OC has to figure out how to use new and strange alien forms that are native to that universe. This could lead to all sorts of adventures as the OC tries to find a way back home.
One interesting storyline could be about Ben exploring new alien forms that were previously unknown in the official series. Maybe he discovers a form that has unique powers that he has to learn to control quickly to face a new and powerful enemy.
Maybe the male OC is from a different dimension where the Omnitrix works in a completely different way. He accidentally gets transported to the Ben 10 universe. His Omnitrix has some unique alien forms that are not known in this universe. He teams up with Ben and Gwen to fight a new common enemy that is attracted to the strange energy his Omnitrix emits. Along the way, he learns about the values of friendship and courage from them.
You could also write a fanfiction where an OC is accidentally bonded with the Omnitrix in a way that it can't be removed. The OC then has to learn to live with it and use its powers for good, but they face challenges as they are not Ben. They might have to deal with people who are suspicious of them having the Omnitrix and also face enemies who are specifically after the device because of its new and unexpected host.
One idea could be that the male OC with the Omnitrix accidentally gets transported to an alternate dimension where the Omnitrix functions differently. He has to figure out how to adapt and use it to get back home. Another plot could involve the OC using the Omnitrix to stop an alien invasion that is targeting his hometown specifically. Maybe the aliens are after the Omnitrix's power source.
Then there's Lyra. She's a female OC who is a brilliant scientist. She reverse - engineers some of the Omnitrix's functions and creates her own power - enhancing devices. She often teams up with other OCs and uses her intelligence along with the Omnitrix's powers to outwit their enemies.
He could have a unique personality trait, like being extremely shy but when he transforms using the Omnitrix, he becomes super confident. For example, if he transforms into a big, strong alien, his normal timid self disappears and he becomes a fearless leader in battle.
One interesting storyline could be about an original character (OC) who is a half - elf with unique magic abilities trying to find their place in the war - torn world of Warcraft. They might struggle between the two sides of their heritage.
Well, in 'the tribe oc fanfiction', there could be storylines about the characters' survival in a post - apocalyptic world. For example, they might have to deal with scarce resources and form alliances to stay alive.
One interesting storyline could be the nanny getting involved in a local community event in the OC. Maybe she helps organize a charity fundraiser and in the process, she forms new friendships and overcomes some personal insecurities. Another could be her relationship with the family she works for evolving in unexpected ways, like she starts teaching the kids some unique skills that the parents are really impressed by.
Another great storyline is when the OC is a tech genius. They help the iCarly team upgrade their equipment and create even more amazing web shows. Maybe they develop a new app specifically for iCarly that allows for more interactive features with the viewers. This not only enhances the iCarly concept but also creates a bond between the OC and the existing characters as they work together towards a common goal.