Sly could use his agility and charm. He might show off some of his acrobatic skills in a non - showy, but still impressive way. For instance, if they are having a gathering in a garden and something needs to be retrieved from a high tree branch, Sly could easily jump up and get it, making it look effortless.
Well, Sly might be really nervous when he meets Carmelita's family. He could try to show his best side, like being extra polite and charming. Maybe he'd bring a special gift, something that reflects his thieving skills in a positive way, like a rare artifact that he's retrieved legally for them.
One common theme is the struggle between their two worlds. Sly being a thief and Carmelita being a law enforcer. Their love has to overcome this huge obstacle.
The human boy might be a lost traveler who accidentally enters the world of Sly Cooper. He is scared at first but quickly adapts. Sly sees potential in him and decides to train him in the ways of thievery. The boy has a natural talent for stealth, which he developed while trying to survive in the wild on his own. With his help, Sly's gang is able to pull off a heist that they previously thought was impossible, stealing a valuable artifact from a heavily guarded fortress.
A fanfiction of Sly Cooper and Carmelita getting married could be full of twists and turns. For example, just as they are about to say their vows, one of Sly's old foes could show up with a plan to disrupt the wedding. But Sly and Carmelita, being the strong characters they are, team up to defeat the foe and then continue with their wedding. Their relationship has always been complex, with Carmelita chasing Sly in the past. Now, as they get married, it symbolizes a new chapter where they are on the same side, facing the future together, and their love overcomes all the past differences and challenges.
In fanfiction, when Sly Cooper meets a fan, the fan might be overjoyed. The fan could ask Sly for autographs or to hear stories of his adventures. Sly, being the charming character he is, would probably oblige and share some of his tales. This encounter could also lead to the fan becoming an important side - character in Sly's next adventure, providing local knowledge or some unique skills to help Sly on his mission.
Sly would probably be initially shocked. But then he'd be overjoyed. He'd start making plans to keep her and the baby safe. He might even consider retiring from his thieving ways to be a full - time family man.
One idea for a Sly Cooper fanfiction involving a human girl could be that she is a skilled thief herself, perhaps from a different part of the world. She crosses paths with Sly and his gang during one of their heists. At first, they are suspicious of her, but she proves her worth by helping them outwit the guards in a highly secured museum. As they continue to work together, Sly starts to develop feelings for her unique charm and courage.
One idea for a Sly Cooper fanfiction involving a human boy could be that the boy is a huge fan of Sly Cooper's adventures. He somehow stumbles upon a relic from one of Sly's heists. This relic has some sort of magical power that transports him into Sly's world. There, he has to learn how to survive among the various animal characters and, in the process, he becomes an unexpected ally to Sly and his gang, helping them outwit the bad guys in new and creative ways.
Archive of Our Own (AO3) is also a great place to look. There are many different fanfictions there, and you can filter the search results to find specifically female Sly Cooper fanfictions. It has a large and active community of writers and readers, so you're likely to find some hidden gems.