Continuity mistake: When Leela says she wants to enroll in to the army Kif is standing right next to Brannigan. When it cuts Kif is gone. (00:02:20)
Continuity mistake: Bender's ID-tag pinned on his chest changes position several times during the episode. In some shots it's even gone. (00:09:50 - 00:13:00)
Continuity mistake: When Leela tells Bender to stop destroying the earth she has her arms crossed. When it cuts they're down. (00:20:40)
Continuity mistake: When Bender is brought into the surgery tent and Zap is holding Nixon, the level of the fluid in Nixon's jar changes between angles. In the wider shots it covers his whole head, in the closer ones the top of his head is above the fluid.
Continuity mistake: When Bender enters the officer's bar, he has two medals on his chest. In the last shot of him they have both disappeared.
Answer: You are thinking about episode 20 of series 2 - "Anthology of Interest I". She technically never kills anyone, but in the episode she ask a "What if machine" (one of the Professor's inventions) what would happen if she was more impulsive. The machine then shows the more impulsive Leela killing off the Professor to get the money from his will and thereafter killing Hermes, Bender, Scruffy, Cubert, Nibler, Amy and Zoidberg to cover it up. Finally she does something really impulsive with Fry.
Andreas[DK]