UrsusArctos: Thus ends the tragedy of Darth Tabris the Assisted Suicide, and thus begins an eternity of headless Kaworu jokes/fanart. Of course, Kaworu gets his head blasted off in Evangelion 3.0 in yet another pathos-inducing scene that calls back to this. At least one instance of pre-3.0 headless Kaworu fanart was mistakenly assumed to be a spoiler and called out in public, spoiling a whole lot of people.
Mr. Tines: Another "seen more than once", with an immediate callback at the start of 25'.
Dr. Nick: ...which also serves as a callback to Ideon's concluding film Be Invoked, which starts with a recap of a love interest's decapitation.