Sometimes ad teams are hired to sell sexy new products, cool gadgets, or hip brands. And sometimes they’re hired to sell milk. Yet a product that could not be more boring, can never really be advanced or improved, and which most of the world already knew existed was magically reinvented 20 years ago when ad man Jeff Goodby wrote two ingenious words, “Got Milk?” One of American consumerism’s most effective marketing campaigns was born. The tagline’s origin is head-slapping in its simplicity—a woman in a focus group said, “The only time I even think about milk is when I run out of it.” Goodby scribbled his response, “Got milk?” and the rest is history. A series of commercials and print campaigns capitalizing on that anxiety—realizing you’re out of milk only after the cereal is poured—enlisted a slew of famous faces to don milk mustaches and ask the iconic two-word question. In honor of the campaign’s 20-year anniversary, here’s a look back at some of the most memorable “Got Milk?” ads.