In Yoda's vision, Dooku mentions that they fought a Terentatek on Kashyyyk. Terentateks are creatures that were known to hunt Force Sensitives. They were first introduced in the video game Star Wars: Knights of the Old Republic (2003).
The 'Jedi fortune cookie' message that opens the show reads "Death is just the beginning."
Barriss Offee makes her only post-arrest appearance in the series during Yoda's vision. Oddly, when listing the Jedi who shouldn't be present (Qui-Gon being dead, Dooku turning to the Dark Side, etc.), he does not make mention of Offee, who was arrested at the end of season 5 for betraying the Jedi and bombing the temple.