The new $20 bill (2003)
Once we all caught up to that darn Pong ad and learned how to get complex animations into banners at a relative low file size cost, creativity in banners plateaued for few years. The industry was concentrating on better messaging, better use of the space, and -- in some more infamous cases -- punching monkeys around.
During the latter part of this time, a new type of ad emerged: rich media. This was a banner on steroids -- one that could get bigger, or float, or have extra pieces called panels. In the early days, those expandables were basically the same banners we'd previously been making with some HTML components that would appear if a user interacted with the banner. Hey -- this was groundbreaking stuff!
Honestly, though, none of it looked very good or was particularly useful. That is, until the U.S. Department of the Treasury decided to release a new, highly advanced $20 bill and purchased a swooping advertising campaign to explain what the bill looked like and contained. A portion of this campaign was a series of expandable banners, but instead of the panels being boring HTML, these were highly interactive, animated, and fully featured. They allowed the user to manipulate a magnifying glass and roll over the different aspects of the bill, with fly-outs that explained the varying security features. For the first time, ads fully realized the potential of this new technology and were a sweeping success. The ads went on to win Yahoo's inaugural Big Idea Chair Award and forever changed the thinking around creating rich media.