When does homage become plagiarism?

Watching Alias always raises a number of questions. Generally they are questions regarding the ridiculousness of the plot. The question on my mind after tonight's episode is "Where is the line between homage and plagiarism?"

This evening's episode involved a substance called "ice-five" that instantly froze whatever it came into contact with. Sound familiar? If you've ever read Kurt Vonnegut's novel Cat's Cradle, it should.

"There are several ways," Dr. Breed said to me, "in which certain liquids can crystallize -- can freeze -- several ways in which their atoms can stack and lock in an orderly, rigid way."

That old man with spotted hands invited me to think of the several ways in which cannonballs might be stacked on a courthouse lawn, of the several ways in which oranges might be packed into a crate.

"So it is with atoms in crystals, too; and two different crystals of the same substance can have quite different physical properties."

. . .

"Now think about cannonballs on a courthouse lawn or about oranges in a crate again," he suggested. And he helped me to see that the pattern of the bottom layer of cannonballs or of oranges determined how each subsequent layer would stack and lock. "The bottom layer is the seed of how every cannonball or every orange that comes after is going to behave, even to an infinite number of cannonballs or oranges."

"Now suppose," chortled Dr. Breed, enjoying himself, "that there were many possible ways in which water could crystallize, could freeze. Suppose that the sort of ice we skate upon and put into highballs -- what we might call ice-one -- is only one of several types of ice. Suppose water always froze as ice-one on Earth because it had never had a seed to teach it how to form ice-two, ice-three, ice-four . . . ? And suppose," he rapped on his desk with his old hand again, "that there were one form, which we will call ice-nine -- a crystal as hard as this desk -- with a melting point of, let us say, one hundred degrees Fahrenheit, or, better still, a melting point of one-hundred and-thirty degrees."

I wonder what ol' Kurt Vonnegut would say.