The McRib, however, often returns to McDonald’s in “the colder seasons” at the end of the year, a McDonald’s executive once explained — the same months that the stock market generally shows stronger returns, a wealth management expert told Investopedia last year. McDonald’s, too, also once said the timing of “McRib szn” is influenced by demand.

Ba da ba ba ba! Arguably, the world's most mysterious sandwich is making a comeback: the McDonald's McRib.