7. Leela's Parents
For almost the show's entire first run, Leela was an alien, the last of her species. But Matt Greoning and David X. Cohen, the show's executive producers, knew different, planning all along that Leela would be revealed as, in fact, a mutant, going as far as sneaking a shot of her parents into an earlier episode "I Second That Emotion." The reveal was made in a season four episode, "Leela's Homeworld". Throughout the episode's runtime, Leela revisited her childhood, reflecting on what it was like to grow up in an orphanarium and never know her parents. Her answers didn't lie in the stars, but deep in the sewers, home of the city's mutated underclass. Born the least mutated mutant of all time, and able to pass for humanoid alien, she was given up by her one-eyed parents for adoption, to have a chance of life outside the sewers. The twist reveal of the identity of Leela's parents was given to the audience early into the episode, viewers having to wait while the purple-haired cyclops caught up, but the final punch was as unexpected as it was sweet. Through a series of flashbacks (as 'Baby Love Child' by Pizzicato Five played), it is revealed that Leela was never really alone growing up, her parents keeping her safe while unseen in the shadows, giving her brief moments of happiness throughout her childhood.