Jim roleplaying the scene where Anakin force-strangles Padme. For once, he's perfectly in character, completely serious, with no silly talk about loot or XP. His roleplaying is so superb that Annie actually asks him to stop for a moment, just to tell him how much she loves him for it.
The planet that Vader destroys not being Alderaan, but NABOO. They manage to write the sequence of strips before it, revealing the identity of Vader early (actually surprising people), making Tarkin a good guy opposed to this (again surprising the crap out of everyone reading the strips) and actually making this sequence go from "We knew this was coming" to a very heartwrenching, "He... he didn't?" moment because for the Darths and Droids readers, Naboo is has been a place they've become emotionally attached to. Oh. And JAR JAR WAS ON THE PLANET. Pete says it best.
Pete:"You. Utter. FRACKKING. BASTARD!"
The GM gets one in episode 778, when his and the players' characters are playing a game within a game: he predicted that Pete's/R2-D2's character would backstab his/Chewbacca's character at the first chance and loot his corpse, so he made sure it would backfire on him by putting a cursed item in his own coin purse.
Chewbacca: Let's discuss how you're going to pay for my resurrection, shall we?
The GM gets another one in episode 796 when Pete declares that he's going to hit the back doors he'd installed on the Peace Moon despite not being around there at all. He triggers an alarm doing so and the next episode has him constantly triggering one alarm after another.
To put this in perspective, Jim, the Cloudcuckoolander of the group, managed to brace a trash compactor with the very trash it was designed to compress, even though Annie had already pointed out how impractical that would be.