In my experience in the Imaginary Invalid, no moment has been as profound and enjoyable as when I, and one of the techies, were asked to decorate the bookshelf that appears in Argon's house. While completing this task we decided to include many details that may go unobserved by those not searching for them. So, here are some Easter eggs on the bookshelf. In order from most obvious to most unnoticeable:
Party skeleton! The most obvious detail that I'm sure anyone who sees the show will notice is the human skull with a birthday hat on top of the bookshelf. Our original idea with this was to make it look like the bookshelf was alive by giving it hands, feet, a heart, and a head. Ultimately, we decided this was too absurd, so we ended up keeping only one hand, the heart, and the skull. This is one of, if not my favorite, details we added to the shelf.
Twilight. Though not as creative as the other secret details on the bookshelf, we still found a lot of humor in including the first three Twilight books on the bottom shelf. These were, in fact, the first three books we chose after running out of prop books and having to use books from the Black Box. However, one of the Twilight books will not appear on the shelf as it was selected by another cast member to be used as a prop in the opening scene. This is one of only two notable books that is used by the cast members in the scene, the other being the Flat Earth book that was originally to be featured prominently on the bookshelf.
10 out of 10. The third and most niche detail that was included on the bookshelf is the row of ten books each titled 'Ten out of Ten'. We thought this would be a humorous play on words after finding an excess of these books in the Black Box. Though the titles are probably unreadable, and the number of books uncountable from the audience, it is still a fun detail for people to be aware of.
These are not the only jokes and Easter Eggs found on the shelf. Almost every book on the bottom row of the shelf is a play on words, play on characters in the show, or joke about events to happen within the show. So I recommend considering viewing the show multiple times in order to better appreciate these subtle details.
I don't have a picture of the featured bookshelf so instead here is a photo of my kittens playing on my bookshelf at home.