Futurama is renowned for its hidden Easter eggs, some that even diehard fans couldn't have picked up on upon first viewing. That's because these little secrets foreshadow events and characters that wouldn't happen or appear until seasons later.
1. Leela's Parents in the Crowd
Leela's mutant parents can be seen standing in a crowd in the season two episode "I Second That Emotion." At this point in the series, Leela's origins were still a mystery. The audience wouldn't learn the truth until the season four episode "Leela's Homeworld," when those same parents are formally introduced.
2. Nibbler's Shadow in the Pilot
Nibbler's shadow can be seen underneath Fry's chair in the first episode, "Space Pilot 3000." Even though the character hadn't been introduced yet, Nibbler's presence in the pilot is explained years later in the season 4 episode ""The Why of Fry," when it is revealed that the critter pushed him into a cryogenic tank. In DVD commentary for the pilot, Matt Groening explains, "What we tried to do is we tried to lay in a lot of little secrets in this episode that would pay off later."
3. Killer Wasps and the Old Planet Express Crew
Speaking of the first episode, Professor Farnsworth retrieves Fry, Leela, and Bender's new career chips from a package labeled "Contents of Space Wasp's Stomach," implying the old crew was killed by space wasps. This foreshadows the season four episode "The Sting," in which we find out that this did in fact happen to the old crew as the new Planet Express gang are almost killed by giant space bees.
4. The Mysterious Number 9 Man
A man wearing a tunic that says "Number 9" appears in the background many times throughout the series. (Here he is in " Bender's Big Score," again in "My Three Suns," in "How Hermes Requisitioned His Groove Back," and also in random crowd shots.) He first showed up in the pilot, but wouldn't play a pivotal role until the 2010 Futurama movie, Into the Wild Green Yonder, a full eleven years (and one series cancellation) after his initial appearance. In the movie, it's revealed that the Number 9 Man is the leader of the "Legion of Mad Fellows," a group of telepaths.
5. Futurama itself was predicted by The Simpsons
The creation of Futurama itself was foreshadowed in the 1993 episode of The Simpsons, "The Front." In the episode, a writer resembling Futurama co-creator David X. Cohen exclaims, "I'm gonna do what I've always dreamed of. I'm gonna write that sitcom about the sassy robot." Futurama (and sassy robot Bender) wouldn't premier on Fox for another six years.
6. The Omission of Fry's Grandfather is for a reason
In "The Luck of the Fryrish," Fry's father tells Fry's brother Yancy that his name (Yancy) has been passed down for generations, from his father's grandfather, to his grandfather, to him, then down to Yancy. He leaves out his own father (Yancy and Fry's grandfather) implying he was named something other than Yancy. This is because in the next-season episode "Roswell that Ends Well," it's revealed that Fry becomes his own grandfather.