The Elder Scrolls
Skyrim - Did You Know Gaming? Feat. Boogie2988
The book "N'Gasta! Kvata! Kvakis!" appears in three of the Elder Scrolls games: Morrowind, Oblivion, and Skyrim. The text seems like pure gibberish, and the game purports that it is an obscure text written in the Sload language by the necromancer N'Gasta.

In reality, the book is a passage written in obfuscated Esperanto. By making a few substitutions to the text, it can be translated back into English. The passage is actually completely unrelated to Morrowind, and seems to be an excerpt picked randomly from the Internet. It concerns the "Kva! Kvak!", which is the newletter of the 'La Ranetoj,' the Stockholm Esperanto Society. Why the developers picked this excerpt to be included in the games has never been explained.