In what seems to be a running theme, this post will likely end with an open-ended question. In sticking with the theme of this post, I'll be a little backwards and open with the question from the end: "What is serviced, from a developer standpoint, by adding stealthy hidden jokes, Easter eggs, etc. to games?"
This question is prompted by a short story that tickled my fancy from earlier this week. An intrepid audiophile noticed that, in the GDC 2011 trailer for Legend of Zelda: Skyward Sword, a reversed version of the "Zelda's Lullaby" leitmotif comprised a significant portion of the theme music. Now, I think this is a totally cool concept, but rather than waxing musical about the nifty-ness of clever use of a theme, I'll address something a little more relevant: where's the beef?
This is a trailer used at a highly-popular industry event for a series that carries both popular and historical appeal. It's probably a safe assumption that this kind of footage gets about as much attention as any kind of game-related promotional media. With all that, this is something that, even in this Internet age, takes two months to notice. If this were part of a scripted ARG, this would be an inexcusably(?) long time for the reveal of a plot point. It seems incredibly prominent for things that are traditionally hidden in the dark corners of a game (that is to say, Easter eggs). It seems placed in such a way that it is almost sure that it was designed to be found, but is that it? Is this just a clever promotional scheme? It seems counter-intuitive to design a theme track to a video game as a one-off promotional item.
I suppose, then, that the question asked at the beginning of the post would be better-phrased as this: "What is serviced, from a developer standpoint, by adding prominent Easter eggs, etc. to games?"
This is something that has served Valve well, notably with their recent Portal 2 ARG. Their use of this kind of material, however, has been serving an end - that is, a drawn-out game that inspires community and media participation. Something like this, though? I honestly can't say that it has precedent. Maybe I'm misconstruing proportions, but it seems like Nintendo's move is one made without a clear end (or an end that is simply a dead stop). It will be interesting to see, as the game's release draws closer, whether this is effectively used as a piece of continual marketing, or if it is as it seems - strangely anticlimactic.