The Old Man and the Big 'C'
Family Guy Season 11 Episode 3 (11/04/12)
Peter, Joe, Quagmire, and Brian all go to a Red Sox game together, and as they scrum for a home run ball, a secret about Quagmire is revealed: he's actually bald. Peter convinces him to accept his baldness, and he radically changes because of it, becoming an aged dullard who sits on Peter's lawn and uses a radar gun to see how fast people are speeding through Spooner Street. The gang then tell him that he's become boring, and get him to go to the hopsital and get a hair transplant from Dr. Hartman.
While at the hospital, Brian overhears that Carter Pewterschmidt, Lois' dad, has cancer and only has two weeks to live. When the family confronts him about this, they find that he's actually quite healthy. Brian and Stewie figure that he's actually a double of Carter, in place to make sure that Pewterschmidt Industries doesn't lose money by finding out their CEO has died. They follow him in and hear him talking about "Specimen Z" – which they discover is not Carter, but actually a cure for cancer, that Carter kept hidden from the world because it's more profitable to treat cancer than cure it outright. Brian and Stewie steal the cure, but Carter gets it back at gunpoint, though Lois seemingly convinces him to reveal it to the world. He does not, and uses a sly magazine profile that hints at his true evil nature to make the Griffins forget what happened.