I spent a fair amount of time scrolling, and still didn’t manage to see everything. What is known about the comic can be found over at explain xkcd, including all the various things you can see in each frame. There’s so much!
Of course, the whole purpose of the comic is an advert for Randall Munroe‘s new book, “What If?“. I’ll most likely be getting the book soon, and reading all about serious scientific answers to absurd hypothetical questions.
Be warned… once you start scrolling, it’s hard to stop. Onwards!