Coworker of mine just passed along this link, in which is hidden this gem:
The entire plot is actually a tweaked version of Hamlet.
The old Mushroom King (King Hamlet) is de-evolved (killed) by King Koopa (Claudius), and it's up to an inexperienced hero (Mario/Luigi) to restore balance to the kingdom by avenging the king. Daisy is Ophelia and Spike and Iggy are Rosencrantz and Guildenstern.
Except, you know, nobody dies.
You know that was getting posted :). Warning, language is not suitable for young ears or eyes.