Brick Joke/Fan Works


 * Heir to the Empire by Ozzallos has a beautifully-executed example which might slip right past an inattentive reader. Early in the story, after Ranma is transformed (slightly) by his possession of, Kasumi admires his girl form's new silver hair and asks if he can give her silver hair, too.  Ranma's response is distracted, bemused words to the effect of "sure, if I can figure out how I got it."  In the last chapter, a hundred thousand words or so later,  visits from the future, stares at Kasumi, and asks "Say, when did Kas-chan dye her hair brown?"
 * In the prologue of Kyon: Big Damn Hero, Kyon compares being hit by Asakura Ryouko to being hit by a speeding minivan. Guess what happened over twenty-five chapters later.