Check out two videos below offering up the theory that Supreme Leader Snoke is atually Darth Plageuis, the Sith Lord that trained the Emperor, Darth Sidious.
The John Williams music scores for the characters are exactly the same -- abeit for one added pitch.
Palpatine told Anakin that he killed Sidious in his sleep. Maybe not?!
"Darth Plagueis was a Dark Lord of the Sith so powerful and so wise, he could use the Force to influence the midi-chlorians to create life. He had such a knowledge of the dark side, he could even keep the ones he cared about from dying."
It's also been said Disney asked a movie podcast to yank mention of Darth Plagueis in their show, which only adds more fuel to the theory...