The '28 pranks later fanfic' might be a creative work by a fan that details 28 different pranks. It could have a plot that builds with each prank, for example, the first few pranks might be simple and innocent, like putting salt in the sugar bowl. As the number of pranks increases, they could become more elaborate and have greater consequences. There could be a character who is the main prankster, or it could be a group effort. The fanfic might also explore the reactions of the victims of the pranks, whether they get angry, laugh it off, or try to get revenge.
Well, without having read it, '28 pranks later fanfic' could be a fan - written story centered around a series of pranks. Maybe it's set in a school where students play 28 pranks over a period of time. Or perhaps it's in a workplace and the pranks are part of some sort of office rivalry or just for fun among colleagues. It could also be in a more fantastical setting like a magical world where the pranks have magical elements to them.
I'm not sure specifically as it could be about all kinds of pranks in a fan - created story. It might involve a character or group of characters playing 28 different pranks on each other or within a particular setting.