What began as a clever marketing campaign has morphed into a viral web phenomenon, and the Old Spice Guy, Isaiah Mustafa, is milking it for all it's worth.

After garnering global fame as "The Man Your Man Could Smell Like" in a series of Old Spice commercials, Mustafa, a former American football player, appeared on Oprah and has signed a talent deal with US network NBC.

The ad that made him famous ... The Man Your Man Could Smell Like.

But it's the web that has really fallen in love with the character, in one of the rare cases where cynical web users have gravitated to a professional marketing campaign designed to spruik a product. Marketers the world over are studying it as a case study on how to manufacture a viral hit.

Mustafa's clips on the Old Spice YouTube channel have racked up almost 55 million views, making it YouTube's most viewed sponsored channel of all time.