GLENVIEW, Ill.—In architecture, form follows function. In pasta, shape follows sauce. Margherite, farfalle and lumache may look like daisies, butterflies and snails, but taste is what counts: which shape combines with which sauce to taste best.

It counts in Italy, that is. In America, the rule has evolved a variation: Shape follows tie-in. That's why macaroni from Kraft Foods looks like Super Mario, Spider-Man and Marvin the Martian—and why Guillermo Haro is the nation's best-selling...