At first glance, Futurama's Phillip J. Fry is an unremarkable young man. Born in the late 20th century, Fry had few prospects in life before being cryogenically frozen for a thousand years. Waking up in the year 3000, Fry quickly made a life for himself, finding work with Planet Express and developing connections with the likes of Bender and Leela. But over the course of the series, the largely unassuming Fry was revealed to have a far more vital role in the future of not just the human race, but the fate of the entire universe.
In Futurama's seven seasons, multiple episodes teased Fry's full role as a savior of the universe, including his ties with Nibbler, the seemingly benign alien pet Leela adopted in the show's first season. Season 3's "The Day the Earth Stood Stupid" revealed Nibbler was actually a member of an ancient race that had long protected the galaxy from threats such as the Brainspawn, a species that harvested the knowledge of all other known races and wiped out all life once they deemed their mission complete. The Brainspawn's greatest weapon was a telepathic ability to dampen the intelligence of anyone they come into contact with, reducing any resistance.
However, Fry was immune to the Brainspawns because of his lack of delta brainwaves. Season 3's "Roswell that Ends Well" showed Fry once went back in time and (following the demise of the man he thought had been his grandfather) actually impregnated his paternal grandmother, inadvertently making himself a unique paradox within the universe as his own grandfather. This made Fry the key to defeating the Brainspawn in "The Day The Earth Stood Stupid," with Fry tricking the Brainspawn leader into leaving Earth.
In Season 4's "The Why of Fry," Nibbler again called on Fry to protect the universe, as the Brainspawn successfully gained all the knowledge they needed to enact their final plan. Fry confronted the Brainspawn once more and was forced to sacrifice himself to drag their entire race into a pocket dimension.
But in one last act of spite, the Brainspawn revealed it had been Nibbler, who had ensured Fry was frozen in the first place. Fry had been prophesied -- due to his lack of delta brainwaves and his ensuing natural resistance to mind-affecting attacks -- as the Nibbloion's fabled "Mighty One." As a result, he needed to live into the 31st century to defeat the Brainspawn and save the universe. Although Fry was briefly sent into the past and given the chance to prevent this outcome (restoring his original life but dooming the future), Fry ultimately decided to save the universe.
However, the Brainspawn weren't the only enemies Fry saved the universe from. His natural resistance to telepathic probes made him the ultimate weapon against the Dark One in Season 5's "Into the Wild Green Yonder." The ancient and malicious Dark One could manipulate almost anyone or learn their next move through its telepathic abilities. But Fry's natural resistance gave him the chance to prevent the Dark One's plans to destroy a dwarf star before it could be reborn as the benevolent Encyclopedia.
Season 2's "Anthology of Interest" also confirmed just how vital Fry's role in the continuation of the universe was. An episode composed of three "What If?" scenarios, "The Un-Freeze of a Lifetime" featured a world where Fry hadn't been frozen. But due to his existence only being technically possible because of a stable time loop caused by his visit to the past (which only occurred due to him having future technology available), the space-time continuum began to crack at the seams.
The Vice Presidental Action Rangers -- led by Al Gore and including Stephen Hawking, Nichelle Nichols, Gary Gygax and Deep Blue -- were able to identify something wrong with reality as a result of Fry's actions and tried to freeze him to ensure the stability of the timeline. But a spiteful Fry destroyed the cryogenic tube, resulting in that version of reality shattering. It was a strong reminder of just how vital Fry -- who many people viewed as a meaningless speck in the overall fate of the galaxy -- really was. Without him, the universe would have crumbled multiple times across the course of Futurama. If Fry had chosen to never go to the future, all of existence could have ended, making him the most important man in his entire universe.