It could be a new, unknown enemy. Maybe someone from a far - off planet who has a grudge against the Saiyans. This character could be really powerful and sees Gohan as an easy target at first, so he throws a punch.
Another possibility is a jealous rival. Maybe there's someone who is jealous of Gohan's power or his relationship with certain characters. This rival could do things to annoy Gohan and push him to the edge of his temper.
There could be. Fanfiction is a creative space where all kinds of wild ideas are explored. However, this particular concept seems rather unorthodox considering Gohan's relationship with Bulma in the original Dragon Ball series. Gohan has always seen Bulma more as an aunt - like figure. But in the world of fanfiction, anything is possible. It might be difficult to find though, as it may not be a popular or widely - accepted concept.
There could be. Fanfiction writers often explore different scenarios for their favorite characters. But keep in mind that these are not canonical. They are just the creative interpretations of fans who want to see different relationship developments for Gohan and Videl.
I'm not sure specifically as I haven't read that particular fanfic. But generally, it might be about a character named Percy getting punished in the form of a spanking within the context of a fan - created story. It could be set in a fictional world from a book, movie or game that the fanfic is based on.
I'm not sure specifically as I don't know the exact 'little gets spanked story'. It could be about a child who gets spanked for misbehaving. Maybe the story details the reasons for the spanking, like breaking a rule or being naughty.
Cell - like characters are often antagonists. Since Cell was such a major foe in the original series, new versions of Cell - like beings could be created in fanfiction to make Gohan angry. They might target his loved ones or the Earth itself, provoking Gohan's rage.
One possible reason could be that Videl does something that endangers herself. Gohan, being protective, might get angry out of fear for her safety. For example, if she recklessly jumps into a fight without proper training or preparation.