I think Claire would be an interesting choice. She's always been a bit of a control freak in the show. So, seeing her deal with a pregnancy, either her own or someone else's in the family, would be really fun. She might try to micromanage everything from the baby shower to the nursery setup.
Manny could also be a good character to focus on. He's such a sensitive and unique character. If it was his mother or step - mother getting pregnant, he could have some really heartwarming and humorous reactions. He might start writing poems about the new baby or trying to give the pregnant woman advice from all the books he's read.
Gloria could be a great character to focus on. She has a strong personality and her own cultural background that could add a unique flavor to a pregnancy story. Her relationship with Jay and how he supports or doesn't support (in a comical way) during the pregnancy could be explored.
Pepper Potts could also be very interesting. If she travels back in time, she could use her business acumen and knowledge of the future Stark Industries to make significant changes. She might also have a different relationship with Howard Stark, influencing the Stark family in new ways.
Loid would also be an engaging character to center on. His spy skills and ability to adapt to any situation could be really cool in the Naruto world. He could use his disguise and infiltration skills to gather information about the ninja clans or even help Naruto on a mission. His calm and calculated nature would be a contrast to the more impulsive and emotional nature of some of the Naruto characters.
I think being reborn as Phil would be really interesting. He's such a fun - loving and quirky character. You could take his already comical personality and add a new dimension to it with the reborn concept. Maybe the reborn Phil uses his new knowledge to be an even better real - estate agent or to come up with even more hilarious parenting ideas.
Djimmi would be really interesting. As a genie, he has a lot of magic powers and a whole magical realm to explore. His character is full of mystery, and his motives can be very complex. You could explore his backstory, like how he became a genie, and what his true desires are. There could be a story about him trying to break free from the constraints of being a genie, and Beppi could be the catalyst for this change, either helping or hindering him.
Mercury from RWBY could be an interesting character to focus on. He has a rather morally ambiguous nature already. In a Darkwatch fanfiction, he could be tempted by the power of the Darkwatch's enemies, like the vampires or demons. His prosthetic legs could also be given some kind of dark upgrade, and we could see him struggle between his own self - interest and the greater good in this new and dangerous setting.
Raphael could be really interesting. In the 2003 version, he is hot - tempered and tough. In the 2012 version, he also has a strong personality. Seeing how he reacts to his counterpart and how they might either clash or bond could be a great focus. Maybe they have a friendly rivalry as they compare their fighting skills.
Arya Stark would be a great choice. You could write about her using her assassin skills to target key military leaders during the war. For example, she could infiltrate enemy camps disguised as someone else and take out important commanders, which would have a huge impact on the battles.
Naruto himself would be very interesting. His energetic and determined personality would contrast greatly with the more laid - back and technology - dependent Jetsons. He could bring a sense of adventure and action to their world, and his ninja skills would be something completely new for them to experience.
Ross could be really interesting. Since he's an archaeologist, in a crossover with a show like 'Indiana Jones' (in a fanfiction sense), he could go on an adventure with Indiana Jones. Ross would bring his academic knowledge while Indy would have the practical experience. Their interactions would be filled with Ross trying to over - analyze everything and Indy just wanting to get the job done.
Rias Gremory would also be an interesting character to focus on. If she were to interact with Ichigo, her leadership skills and her own goals within the Highschool DxD world could be influenced. Maybe she tries to recruit Ichigo for her peerage, which would lead to all sorts of conflicts and negotiations.