One key element could be family. Thanksgiving is often a time for family gatherings, so Brian might have had a special time with his family. Another could be food, like a traditional Thanksgiving turkey.
A major theme is identity. Since she is a female version of Piccolo, she has to come to terms with who she is compared to the original Piccolo. Family also plays a role. In some fanfictions, she might be searching for her family or creating a new family of her own. Additionally, the theme of good vs. evil is common, as she battles against various villains.
Piccolo's back story in Dragon Ball Z has several important elements. Firstly, his race as a Namekian which is known for its strong warriors and unique abilities like regeneration. His start as a sort of anti - hero, being born from the remains of King Piccolo with the intention of getting revenge on Goku. Then, his journey of self - discovery and change as he witnessed the power of friendship and unity among the Z - fighters. He also played important roles in some of the major battles, such as against the Saiyans, where his power and strategic thinking were crucial. All these elements together make up his complex and interesting back story.
One great piccolo and oc fanfiction could be about an OC who is a trainee under Piccolo. The OC learns martial arts and self - discovery from Piccolo. Another could be a story where the OC has a special power that Piccolo is interested in and they form an alliance to protect the earth. And there could also be a fanfiction where the OC is from another dimension and Piccolo has to help the OC get back home while they face various challenges together.
Training is also a popular theme. Since Piccolo was Gohan's mentor for a while, fanfics often show them training together and Gohan achieving new levels of power with Piccolo's guidance. There are also themes about family, as Piccolo becomes like an honorary family member to Gohan. He protects Gohan and is there for him in a way that is similar to a family member, and this aspect is often explored in fanfics.
One possible theme could be growth. Gohan has always been on a journey of growing up and Piccolo has been part of that journey. In the fanfiction, this growth could be explored in a more personal and emotional way, perhaps related to their relationship.
One acceptable theme is their relationship in terms of power balance. How Piccolo's different forms compare to Cell's various stages of evolution. Also, the psychological aspect of their encounters, like how they perceive each other as opponents, can be a great theme for fanfiction.