Three Hundred Big Boys - S5-E11
Continuity mistake: Right before Leela dives into the whale tank, she drops her snorkel and mask, but when the shot pulls back, they've completely disappeared.
Three Hundred Big Boys - S5-E11
Continuity mistake: When Bender is being filmed stealing the cigar, we see the "robocop" showing the footage on his screen. In the wide angle you can see he has the siren on top of his head, then in the next shot it's suddenly not there. Then he actually raises it out of his head in the final angle.
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]