So this was just an idea I had. Depending on the reaction to this story, I may or may not continue. So, PLEASE review with your thoughts. Comments are always appreciated.
Kili really could help himself. He knew that he shouldn't do it, and he also knew the trouble that he would get into for doing it. But, he also knew that the look on Thorin's face when he realized would be worth it. So, the youngest dwarf went ahead and did it anyway. Of course, Fili had the chance to hold him back. Fili could have stopped it if he had felt so inclined. After all, they were sharing the watch together. But, let it never be said that Fili was not averse to playing a good joke on their uncle. Thus, the first rule came into existence.
Braiding buttercups into Thorin's hair while he is asleep is not allowed.