A common theme is Arthur learning a lesson. When he gets grounded, it's usually because he did something wrong, like lying or being disobedient. Through the experience of being grounded, he grows as a character.
Well, in some 'arthur gets grounded fanfiction', Arthur gets grounded for coming home late. He then realizes the importance of following the rules and respecting his family's curfew.
A 'trunks gets grounded fanfiction' might explore various aspects. It could be about Trunks, a character from a particular series, getting punished by being grounded. This could lead to different scenarios such as how he copes with the restrictions, his relationships with other characters during this time, and his internal thoughts and growth. Maybe it shows his struggle between his normal adventurous self and the confined situation he's in now.
The most interesting part could be Trunks' attempts to break the rules of his grounding in a clever way. He might use his unique skills or intelligence to find loopholes.
Well, of course, Caillou himself is the central character. His parents also play important roles as they are the ones who ground him and teach him lessons.
Perhaps Seto got into a fight with a powerful enemy and in the process, he put others in danger. His guardians or the people in charge decide to ground him to teach him a lesson about responsibility. During his grounding, he could start to reflect on his actions and come up with new strategies to face his enemies. He might also discover new things about himself while being alone in his grounded state.
In the fanfiction, Angelica could get grounded for lying to her parents. For example, she tells them she's going to a friend's house but actually goes to the park instead. Her parents find out and ground her. This would lead to her having to stay at home while the other kids are having fun outside, which could be a source of conflict and growth for her character.
One possible plotline could be that Harry gets grounded for accidentally using magic outside of school in a Muggle area. This might lead to him having to deal with the disappointment of his friends who can't visit him as easily. Another could be that he gets grounded because he was caught sneaking out to follow a lead on a new dark wizard threat, and the adults in his life want to keep him safe by restricting his movements.
Obviously, Harry Potter himself is the central character. His friends like Ron Weasley and Hermione Granger are also often involved. They might try to visit him while he's grounded or come up with plans to get him out of being grounded. Dumbledore could also play a role, either as the one who enforces the grounding in some cases or as the one who might offer some wisdom to Harry during his time of confinement.
Maybe in the fanfiction, Caillou gets grounded for breaking his sister's favorite toy. He then spends his time grounded trying to fix it as a way to make amends, which shows his growth in taking responsibility for his actions.