Time Keeps on Slipping - S3-E14
Continuity mistake: In this episode, Fry loosens his helmet and his head expands immediately. But, in the first episode, a man on the Moon takes his helmet off for several seconds and his head never expands.
Time Keeps on Slipping - S3-E14
Continuity mistake: After the end of the basketball game, Leela's tights briefly disappear. (00:07:35)
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]