It takes only 30 seconds of footage or a leaked production shot to send Game of Thrones viewers into a tizzy of wild theorizing. In fact, it seems as if a new fan theory sprouts up every week. It's hard to know what to take seriously, and what to write off as wishful thinking. But there are a few fan theories that have been around for years — 20 years, in this case. One of the longest-standing, most credible, and widely believed fan theories was actually born by the earliest GoT readers in 1996, when George R.R. Martin published the very first book in the series, A Game of Thrones. Now, all signs indicate that this particular theory, about our boy Jon Snow, is about to be addressed in Sunday night's episode. It's a big one that pieces together a lot of background information and book-only material, and you're going to want to know the 4-1-1 beforehand. [SPOILER ALERT, duh].