It is a well known fact in the entertainment world that half of any success acheived with any show is due to good casting. Not to mention the fact that half a directors' job is to cast a perfect show, whether it runs for nine days, nine weeks, months, or in "I Love Lucy"'s case, nine years. A show can have brilliant writers, directors, editors, and other technicians, but if something in the casting doesn't work, chances are the show won't either.
However, if the casting is just right, everything seems to fall into place. And thus we arrive at the perfection of the casting of "I Love Lucy". Now it can of course be argued that without "I Love Lucy"'s brilliant writing team, the show would not be what it was and continues to be, but there is no denying that the combination of the four stars of the show is what gave it it's ultimate lasting power. In his autobiography, Desi Arnaz likened the success of the show to inventing and patenting the perfect formula, much like a company like Coca Cola did with their product. All they did, he said, was find the ideal combination of ingredients, mixed them together just right, and finished with the ideal product.