Art & Copy via the New York Times:

[The film] not only examines how seminal campaigns were born, but also, in the case of “Got Milk?” and others, how they almost died premature deaths…in the case of the former concept, people at Goodby, Silverstein thought it was lazy, not to mention grammatically incorrect.

“It’s clunky. It’s not even English,” recalls Mr. Silverstein in the film, expressing his initial distaste for the idea. He later gleefully adds, “It worked!”