Continuity mistake: When Lucy Lui shines the projector at the evil Lucy Lui you can see the movie running. How is that possible if the projector is not pointed at the screen?
Character mistake: Lucy Liu-bot says Fry's name normally, but uses an automaton voice for "Can eat more", when she has always used Fry's name as a Text-to-speech type of automaton voice. (00:07:45)
Continuity mistake: When Fry and Lucy Liu-bot are in Dinkin Donuts, Fry has a jam doughnut with a bite taken out of it. Fry and Lucy Liu-bot talk and Lucy Liu-bot explains about her personality and it cuts back to Fry, who has a complete jam doughnut and takes a bite out of it. (00:08:00)
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]