This features one of the greatest 'shy virgin to rampant slut' transformations I've ever seen. The plot is simple, but it does everything it needs to. It sets up why our lead is suddenly gagging for it, then (after just a little cockteasing) his more experienced best friend steps in to help.
The dialogue is impressively true to the show and even finds ways to incorporate both of season 1's most memed pieces of dialogue in a fairly organic way. Both our leads express themselves well throughout; Mark starts nervous and desperate, only to embrace the pleasures of the flesh with the fervour of a zealous convert, while William carries his trademark sense of humour and the experience of a guy who's been around the block a few times (and Omniman's short appearance sees him spitting truths without restraint or shame).
The fact that both our leads are hot and hung is certainly a nice bonus to the ensuing sex scene, which has plenty of variety in terms of positions and techniques on display.
While there is definitely room for a sequel here, this chapter by itself is tells a complete story on it's own and is absolutely worth a read if you want something hot and funny.
Fun Fact: Reading this is why I went to watch the show it's based on.