One common theme is power struggles. Since Black Goku is a very powerful character, when he crosses over, there are often battles to determine who is the strongest in the new combined universe.
Time - related themes are also common. Given that Black Goku's existence is somewhat related to time - travel and alternate timelines in the original story, in crossovers, his presence can mess with the timelines of the other universes he crosses into. This can lead to stories where characters have to fix the timeline while dealing with Black Goku's actions and motives.
Power comparison is a common theme. For example, when Goku crosses into the Marvel universe, fans often like to see how his Saiyan powers stack up against the likes of Thor or Hulk. Another theme is culture clash. When Goku enters a different fictional world like the world of Bleach, his Saiyan values and the way of life in Soul Society are very different, and this contrast is explored in the fanfiction.
Many female Goku Black fanfictions revolve around the theme of redemption. Given that Goku Black was originally a villain, the female counterpart may also start off on the wrong foot. Writers like to explore her journey towards redemption, changing her ways and perhaps even becoming a hero. Additionally, themes of friendship and rivalry are common. She might form new friendships or rivalries with other characters in the Dragon Ball world, which adds depth to the story.
A common theme is power and corruption. Since both characters are power - hungry in different ways, many fanfictions explore how their thirst for power corrupts them further. For example, they might go on a rampage across different universes to gain more power.
Love and redemption can also be common themes. Sometimes the harem members help Goku Black to find a new path or redeem himself through their love. It adds an interesting layer to his character.
Common themes include power imbalance. Goku black is extremely powerful compared to Bulma, so how they navigate that in a relationship can be explored. Another theme is the transformation of Goku black's character through his interaction with Bulma. Sometimes, there are themes of sacrifice, like Bulma having to sacrifice something for Goku black or vice versa. There can also be themes of mystery, as Goku black has his own secrets and motives, and Bulma tries to figure them out within the context of their relationship.
One common theme is the battle of wills. Goku Black and Vegeta are both strong - willed characters, and fanfictions often explore how they clash or come to an understanding.
One common theme is the clash of cultures. Goku's Saiyan heritage and Black Widow's Earth - based spy world are very different. Another is the power combination. They both are very powerful in their own ways, and fanfictions often explore how they use their powers together.
A common theme is power - seeking. They are often depicted as constantly striving for more power and ruling over the universe. Another theme is their unique bond, whether it's a friendship or a more sinister partnership.
One common theme is the clash of different cultures. Since Goku is from a very different world, when he's in a crossover romance, his Saiyan culture often clashes with the other character's world. For example, his straightforwardness in expressing emotions might be different from the more reserved nature of some other characters.
One common theme is the exploration of different power dynamics. When Black Lightning crosses over with other heroes, like in a crossover with Batman fanfiction, their powers interact in various ways. Another theme is teamwork. They have to learn to work together despite their differences.