When Charlie first examines the ancient computer, she exclaims "Sweet Ada Lovelace!" Ada Lovelace was an early 19th century British countess and mathematician who worked on a prototype computer, the Analytical Engine, and is considered the first computer programmer.
On Charlie's tablet desktop is a picture of Lying Cat, a character from the comic series "Saga" (Charlie wore a Lying Cat t-shirt in Pac-Man Fever (2013)), and an image from the cover of the Supernatural book series. The opening screen of the tablet has a map of Moondoor, the LARP game presented on LARP and the Real Girl (2013).
Crowley calls the Wicked Witch "Miss Defying Gravity." This is a reference to the Broadway musical, Wicked, which is a prequel to The Wizard of Oz about how Elphaba (the Wicked Witch) became evil. One of the most famous songs from the musical is Defying Gravity, sung by Elphaba.
Charlie mentions that beckywinchester176 (referring to the recurring character Becky Rosen who was briefly Becky Winchester when was married to Sam in the episode 'Season Seven, Time for a Wedding!') uploaded all the unpublished supernatural works to the internet. This episode is number 176 of the series.
If it's the Wizard of Oz books that are supposed to be a guide, then the shoes should be silver instead of red. They were changed in the movie to take advantage of the color film.