"Sacrifice" (fourth of a four-parter season finale)
Tropes:
Arbitrary Skepticism: The idea that someone can return from the Force to communicate with the living is met with equal skepticism from Ki-Adi-Mundi, despite the fact that the Jedi regularly use Psychic Powers granted to them by the Sentient Cosmic Force. Justified in that belief in the Force explicitly renders spirits impossible, as all beings become one with the Force when they die.
The Bus Came Back: Chancellor Valorum and Qui Gon-Jinn'sforce ghost come back for this story arc. Sifo-Dyassort of comes back for this story arc, and most major characters within The Clone Wars cast itself (Anakin, Obi-Wan, Ahsoka, Rex, Dooku, Mace, Artoo, and Sidious) pop up at varying points or another.
Book Ends: At the time of airing, anyways. The Clone Wars began with Yoda being the first major character featured, and it ends with him being the one to take center stage in the final story arc of the series. Subverted once the seventh season came out, though Yoda does have a role in that one as well.
Call-Forward: Towards the events that lead to the Original Trilogy.
Grand Finale: At the time it was released, the arc was the finale for The Clone Wars. It ends up being a case of Series Fauxnale due to the release of the seventh season of The Clone Wars.
Two-Part Tetralogy: The first episode focuses primarily on the Sifo-Dyas conspiracy and doesn't give quite as much focus to Yoda as the later three episodes, which all deal much more with Yoda discovering how to manifest consciousness after death, like Qui-Gon before him had attempted to do.