1) (Not exactly sure of the wording)
Han in EPV: I don't have time to discuss this in a committee
(escaping from asteroid slug)
Amidala in Ep1: I was not elected to watch my people suffer and die while you discuss this in a committee! (addressing the Senate)
2) R2 in EPVI: R2 gets hit by a stormtrooper trying to open the shield bunker and goes nuts
R2 in EPIII: R2 "distracts" General Grievous when Ani and Obi are captured and sent to the bridge.
3) In EPIII: Palpatine's confrontation with a great Jedi ends with Anakin joining the dark side
In EPVI: Palpatine's confrontation with a great Jedi ends with Anaking leaving the dark side