Reaper Man/WMG

WMGs for Reaper Man.

Reaper Man is a novelization of the song "Particle Man".
First off, Terry Pratchett is a very big fan of They Might Be Giants. Then there's the similar titles and the fact that the book was released in 1991, one year after the song. But, there's a lot more, and nearly every line in the song is referenced. Warning: Contains lots of spoilers.
 * Death is Particle Man. He's often referred to as "Little Death," and he "does things a particle can," like passing through solid objects and appearing in two places at once (spooky action at a distance). The book is about the problems that come up when he develops a personality of his own, or, in other words, "What's he like? It's not important." Particle Man.
 * The Auditors are Triangle Man. They always exist in threes, and they hate both Particle Man (Death) and Person Man (Humanity). They manage to get Death laid off at the start of the book; in other words, they have a fight, Triangle wins. Triangle Man.
 * Obviously, Azrael is Universe Man, as he is, indeed, the size of the entire universe, man. He's usually kind to smaller man, a reference to his taking Death's side. He has a clock with a minute hand, a millennium hand and an eon hand, and when they meet, we can presume that it will be happy land. Powerful man. Universe Man.
 * Even more obviously, Humanity as a whole (and Windle Poons in particular) is Person Man. He doesn't get hit on the head by a frying pan, but he has lived his whole life in Ankh-Morpork, which many would be willing to describe as a garbage can. As well, there's is a lot of questioning whether or not Windle Poons is depressed or if he's a mess, and does he feel totally worthless. And the big question about the book is how he got into that state, or, "Who came up with Person Man?"

That's about it. It's a short song.

Azrael is actually Tengen Toppa Gurren Lagann.
A being so vast that nebulae are merely the glint in his eye? Yeah, that sounds like a ten million light year tall super robot to me. Basically, after the end of the events of Gurren Lagann, the residual badass left over from the battle with the Anti-spiral was so powerful that the Tengen Toppa Gurren Lagann became self aware and integrated itself into the very fabric of reality.
 * Alternatively, Tengen Toppa Gurren Lagann was Azrael's physical form, which the main characters were able to summon to their universe and command through the sheer power of their own badassery.

The Auditors are Anti-Spirals.
They believe organic life needs to be destroyed, and Spiral Energy plays into the whole power of belief thing.
 * And at some point someone will find and use the fifty-foot-high killer golems mentioned in Making Money against them. Yes, the golems exist. Ms. Dearheart just isn't digging deep enough.
 * Does this mean that Vimes will play Kamina? Because that would be ing awesome.
 * Actually I would think that Vimes might be Kamina's father, leaving his family because he doesn't want to burden them with his imminent death perhaps. Or, more fitting still, Carrot's son. A man people follow even if they're not sure why? A man who exhorts you, not to believe in yourself, but to believe in him, because he believes in you? That's so completely Carrot's whole being that I almost think that Carrot somehow manages to be in both universes simultaneously.

The hourglass that Bill Door picks up from the desk in his dream was Ysabell's.
He doesn't know Miss Flitworth well enough (yet) to react so strongly to her mortality, and there was more than one lifetimer on the desk, suggesting that it was Ysabell's and Mort's pending and simultaneous deaths that his psyche was processing. It's probably Ysabell's, not Mort's, because Mort and Death didn't part on such good terms, so Death wouldn't regret his ex-apprentice's demise as much as his adopted daughter's. Plus, conversing with Miss Flitworth had reminded him of Ysabell, whom he had enough understanding of mortality as Bill Door to grieve for.
 * As Reaper Man takes place no more than a couple of years before Soul Music, it could well be Death's awareness that he'd soon have to perform the Duty for Ysabell that'd left him so distracted, the Auditors were able to petition Azrael to retire him in the first place. This makes his last words to Miss Flitworth's fiancee a case of Fridge Brilliance: it's an indication that he's accepting how his own daughter and son-in-law, too, will be going on to the afterlife together.