251. "Superman: The Oldest Man in Metropolis", "Congo Bill: Congorilla Outlaw", "Tommy Tomorrow: The Giant Amoeba of Space"

Clark Kent is sent to the the Metropolis Research Center to interview Professor Vance, a scientist who is trying to invent a serum that will increase a human's life span, but is afraid to test it on a person to see what will happen. Clark brazenly consumes the serum figuring that his Kryptonian biology would prove immune to the serum's effects, and keeps a small sample to analyze at his Fortress of Solitude.