Who is Ferris talking to?
I know that breaking the fourth wall is a moviemaking and theatrical gimmick, and that's fine.
In a different kind of story, it wouldn't really even matter much, and it's meant to be kind of 'abstract', not really having a specific individual that the character talks to.
But in this movie, I started wondering about it - if he's talking to some kind of a documentary television crew (which is even amplified by the fact that he feels ashamed enough in the shower scene to try to stop the camera from filming, or something), then .. what happens, when his parents see his 'tricks to faking out the parents' (I am paraphrasing, can't remember what it really was)?
I mean, if he's talking to a TV crew of some kind, obviously the documentary will be aired at some point, and he'll probably want to record it, as he does star in it (who wouldn't?), so it would end up existing in the house, and it'd be just a matter of time until the sister at least would stumble upon it, and show it to the parents, etc.
However, if there is no TV crew, all this behaviour becomes a bit peculiar. Is he just talking to empty air, and trying to get the empty air not to film him?
What's the "in-movie Universe"-explanation for who he is talking to?
The more you think about it, the more questions it seems to raise, and the more odd and unexplained the whole thing seems.
I don't think it's a good idea to break the fourth wall or have narration in a movie. You can SHOW things rather than narrate, and the whole fourth-wall breaking only serves to confuse the plot, at least in a movie like this, where it's paramount that the parents remain completely ignorant and clueless about the real motives, and real events.