The Sith use red lightsabers in honor of the Sith species and the surface and sky of Korriban.
Many believed that Darth Vader was of the Sith species.
Palpatine used mind-tricks on his advisors to make them think that he was a puppet ruler and that they were in control.
One of the plays performed at the Galaxies Opera House is “Shen and Rahasia”.
The Nagai call Palpatine “Emperor Sheev I of Skyriver”.
Sion and Nihilus were training each other in the Trayus Academy when the Mass Shadow Generator went off and turned them into the undead beings we know them as.
Hego Damask was known as “The Wolf of Muunilinst”.
Duel of the Fates is Dathomir’s national (planetary?) anthem.
There’s a holofilm called “Night of the Living Rakgouls”.
The Tales of the Jedi comics are the contents of the Jedi Holocron seen in Dark Empire and Jedi Academy: Dark Apprentice.
The Korriban Sith don’t recognize the Banites as “Sith”, but Vader went through the trials and got knighted by them on his own, hence the scene in Empire’s End.
Exar Kun let the Rebellion use his temple as a base because he hated Sidious.
Shortly after ROTS, Vader built E-3PO to do the things that C-3PO did for him when he was Anakin.
There is an Imperial propaganda film called “Clone Madness”.
Tessek was Tikkis’s accountant. When Tikkies died, Tessek fled to Tatooine.