Deliberate mistake: The fossilised dog looks like the dog did when he was young; it should look old and decrepit, as the dog was when he died. (Presumably deliberate, to avoid a spoiler.).
Futurama (1999)
1 deliberate mistake in season 5
Starring: John DiMaggio, Katey Sagal, Tress MacNeille, Billy West, Lauren Tom
Continuity mistake: When Fry first meets Leela, there's a panel on the wall beside him. It has one red button at the bottom. In subsequent shots it has two buttons. (00:03:50)
Trivia: The robot devil is voiced by Dan Castellaneta, the voice of Homer Simpson.
Answer: Yes Leela knew from early on that Fry had feelings for her. They were pretending to be a couple in 'A Flight to Remember' from season 1 and Fry tried to get on dates with Leela ever since. She just didn't show signs of the feelings maybe being mutual before some of the later episodes.
Andreas[DK]