The current internet opinion is that Snoke is Darth Plagueis.

Initially I scoffed at this idea. I've read the book "Darth Plagueis" and it's a detailed account of his life and how he trained Darth Sidious. Sidious eventually got him drunk and then tortured him to death before declaring himself the Sith Lord.

So why do people think that Snoke might be Plagueis?

1. It's difficult to introduce an external new character to the series who will be taken seriously and on the same level of great Sith Lords, who trained through an elite system that passed their knowledge of the dark side down for millenia, and personally spent all their time training one person to be as powerful as possible. We saw this power in the form of Maul, Dooku, Vader and finally Palpatine. It's not likely that in the 30 years since the Battle of Endor that some random person could become as knowledgeable, skilled and powerful as Sidious, Bane or others. The writers have to introduce someone very great indeed which is why SW fans initially thought that Snoke would have to be Sidious or Plagueis reborn.

2. There is a specific musical score that is played when Palpatine tells young Anakin about Darth Plagueis the wise in Episode 3. This score is never played again in any of the six movies but is played in Episode 7 whenever Snoke is present.

3. This concept art for the new movies (http://i.imgur.com/nzEt0s0.jpg) shows a dark jedi who resembles Plagueis. Plagueis was severely injured by an assassination attempt and had to wear a respirator for the rest of his life. It has been suggested that the girl is Rey and that the man on the ground is Luke or Ren. This is concept art, so not very accurate, and while some people believe this is evidence of Plagueis, others have stated that this was merely the original drawing of Kylo Ren. Snoke has no respirator but he is holographic and he may be in some sort of chamber similar to Vader's that allowed him to be function without assistance.

4. This spanish magazine that detailed the characters of the movie (http://i.imgur.com/7FYl4hw.jpg) shows Snoke. He does not resemble the Snoke in the movie but is very similar in appearance to the original Plagueis. Even if you can't read Spanish you can see that he is played by Serkis, as we know Snoke is. Snoke is clearly a Muun in this picture.

5. Plagueis was a Muun and they were about 8 feet tall and lived for at least a hundred years. Therefore it is possible that Plagueis has been alive since he trained young Sidious. Plagueis was born at most 147 years before the battle of Yavin making him about 170-180 years old if he is in his original body. Serkis has been shown to be wearing extensions and other digital items implying that although Snoke is humanoid, he has longer limbs and may well be Muun.

6. Snoke has a major gash in his face as well as other deformities/injuries around his mouth. Sidious tortured him to death with Force lightning and this is considered to perhaps be scarring.

7. Plagueis was the first (and last) Sith to openly state that he does not support the rule of two and that he wanted the Sith to grow. This is why he allowed Sidious to train Maul, though Sidious had other plans (in truth it is revealed that Sidious never considered Maul strong enough to ever ascend but this is another issue). More importantly, it is why Snoke has allowed the Knights of Ren to form. They are all clearly force adepts, although weakly but he is definitely a proponent of a dark side army to rival the Jedi. Snoke also talks like a Sith implying that the rise of the Jedi is a major threat to them - very very similar to Sidious and his conversations with Vader.

8. Plagueis is the only Sith Lord in known history who could control the midichlorians. He killed and resurrected another Sith apprentice (Venemis) several times to practice his abilities. He did many experiments on living things. Sidious slyly alluded to the fact that Plagueis was scared of his own death, and he couldn't save himself despite his powers. However, perhaps he could, and did.

Okay so what is the popular theory out there?

Many people believe that Plagueis was killed by Sidious, or he was not.

In the event that he was killed, he used his dark powers to resurrect himself at a later stage. Plagueis knew that Sidious was a Sith of significant power and ultimately if he faced him again, he would lose and Sidious would eventually use the Force to destroy him permanently. He recognized that Sidious exceeded him in power. He therefore decided to let Sidious build the Empire until he was killed. We know that Plagueis foresaw the fall of Sidious when he heard about Anakin Skywalker, and Plagueis panicked and asked whether the discovery could have ruined the Sith. He said "Are we undone?" to Sidious. He foresaw Sidious' demise at the hand of a man with Vader's mask. He knew Sidious would die - he'd bide his time and then resume the leadership again. Naturally he pounced on the descendant of the chosen one.

Alternatively Plagueis did not die. Plagueis was one of the greatest Sith who ever lived regarding illusion. Sidious himself admitted that he could be held at the mercy of Plagueis' illusions and couldn't tell if they were real or not. Plagueis therefore could have projected that he was dead, but was alive. Sidious left then Plagueis recovered - severely injured by the Force lightning and permanently scarred. He then went underground for decades.

There are other subtle alternatives to these theories. Many believe that he could control his midichlorians absolutely and existed as a spirit until Sidious died, and then he infused himself into a corpse or other creature to become Snoke.

Another very eccentric theory is that Plagueis foresaw his death and transferred the majority of his midichlorians and actually created Skywalker. Remember Anakin was created immaculately. Plagueis actually did try to create life at one stage with Sidious, and the Force rebounded and all his experimental creatures became diseased. He believed the Force would resist this most unnatural act. However, without Sidious' knowledge he got it right (we don't know) with the midichlorians and didn't really resist his murder in his now weakened state. When Vader died the midichlorians were released and moved along back to the vessel chosen by Snoke.

All of these theories are very impressive and very convoluted. The implications are really massive - that someone was clever enough to use even Sidious as a pawn in a scheme that took at least 50 years to come to fruition. The villain of the new trilogy would then be someone truly memorable.

There are detailed Youtube videos to extrapolate all these points.

Thoughts?