One common theme is friendship. The oc might befriend Chi Chi and they could go through different experiences together, like helping out in the village or training. Another theme is adventure. The oc could join Chi Chi on a journey to find something, like a special ingredient for a meal or a lost artifact in the Dragon Ball world.
Love and family are very common themes. Their relationship as husband and wife, and as parents to Gohan and other children is often explored.
Family is a common theme. Since they have a family in the Dragon Ball series, fanfictions often explore how they raise their kids. Another theme is love, of course, showing the depth of their relationship.
Power struggles can also be a common theme. Dark Goku is often depicted as very powerful. Chi - Chi, on the other hand, has her own strength in terms of her determination and will. The power dynamic between them can create interesting scenarios in the fanfic. There could be moments where Chi - Chi has to find ways to stand up to Dark Goku, or Dark Goku might try to use his power to manipulate or control her in some way.
Love and family are very common themes. Since they are a married couple and have a son, many fanfics explore how they navigate their relationship while also raising Gohan. For example, in some fanfics, Goku tries to be a better husband and father by spending more time at home.
One common theme is the exploration of the characters' backstories. Since the show has a rich set of characters, fans often like to write about what happened before the events of the series. For example, how did the main characters come to be part of the Tai Chi Chasers in the first place.
One place to find chi chi and oc fanfiction could be on fanfiction.net. There are often various stories there that might involve Chi Chi and original characters. You can search by using the relevant tags and browse through the available works to discover ones that seem interesting.
One common theme is self - discovery. The main character often discovers new things about himself through his practice of Tai Chi. Another theme is the power of tradition. The fanfiction usually shows how the ancient art of Tai Chi has a great impact on the character's life.
It could lead to a completely different dynamic in the Dragon Ball universe. Maybe their combined parenting styles would shape Goku and Vegeta's kids in unique ways.
Maybe in this fanfiction, Goku realizes that he and Chi - Chi have very different personalities. Chi - Chi is often more concerned with family and a stable life, while Goku is a free - spirited adventurer. This clash of values could lead him to decide not to marry her. For example, Chi - Chi may want Goku to stay at home and help raise Gohan, but Goku is eager to explore new planets and fight powerful enemies.
One reason could be his pursuit of stronger opponents. Goku is always eager to test his strength and find new challenges. In fanfiction, this might lead him to leave Chi - Chi to travel the universe in search of the toughest foes. He might feel that staying at home with his family restricts his growth as a fighter.