Stan Lee hated one story enough to proclaim it would never be reprinted. The story arrived in Marvel Spotlight #31, which cleared up the matter of Nick Fury’s seeming agelessness once and for all.
The character made his debut in 1963, appearing regularly in the war book Sgt. Fury and His Howling Commandos. Created by Stan Lee and Jack Kirby, Nick Fury was quickly folded into the then-current setting of the 1960s after making an appearance in Fantastic Four, where he was revealed to be working for the CIA. Not long after, the '60s Nick Fury was given his own feature in the anthology Strange Tales, where he was recruited into the clandestine spy organization SHIELD. Nick Fury became a fixture of the burgeoning Marvel Universe, eventually taking over as the leader of SHIELD and becoming Marvel's best spy. But as the years went on and Marvel Comics continued to grow, the problem of Nick Fury’s age soon became a major continuity issue. The creators could get away with it in the 1960s, but soon realized they’d have to provide an explanation for why the WWII veteran seemingly didn’t age.
That explanation came in 1976, with the publication of Marvel Spotlight #31, featuring the Nick Fury-led “Assignment: The Infinity Formula.” Written by Jim Starlin and beautifully illustrated by Howard Chaykin, the story sees criminal mastermind Steel Harris killing one Dr. Berthold Sternberg, the inventor of a serum called the Infinity Formula. Fury had come into with Sternberg during WWII after being injured by a land mine. Sternberg saved his life by injecting Nick Fury with the Infinity Formula, but the serum has a side effect: unless he takes an injection every year, Fury will age rapidly. Fury has to scramble to track down Steel Harris so he can get his yearly injection of the Infinity Formula, and thus keep from succumbing to the effects of rapid aging.
It seemed like Marvel had finally found a way to explain Fury’s slow aging process, but not everyone was happy with the results. According to writer Jim Starlin, Stan Lee hated the story, primarily because it showed Nick Fury to be more morally ambiguous than he thought the character should be. “I had Fury embezzling funds so he could get this formula that would extend his life,” Starlin is quoted as saying in Marvel Comics: The Untold Story by Sean Howe. “Stan was so upset by it he said it would never be used in Marvel continuity, or ever reprinted.” It’s interesting that Lee would object to this portrayal of Fury, as that moral ambiguity would in time become the character’s defining trait. As the ultimate spy, Nick Fury lives in the gray area between right and wrong, frequently using deception and manipulation to accomplish his goals.
Despite Lee’s ultimatum, the story would become official continuity, eventually becoming the de facto explanation for Fury’s agelessness for the next couple of decades in Marvel Comics. For even though co-creator Stan Lee may object to his “unheroic” characterization, Marvel's ultimate superspy Nick Fury works best when operating in the morally gray world of espionage.
Source: Marvel Comics: The Untold Story by Sean Howe
