“The starting point was the question, ‘What happens, when a woman wears a Wonderbra?’” says Joern Welle, executive creative director at Publicis Frankfurt, which came up with the ad.

“Then it was just a small step and a little bit of dramatization from the merely optical effect to a physical one.”

Indeed.

The result was what looked at first glance like your standard ad for the bra, which has built its image around giving women a flattering lift.

You see a poster of a woman in a Wonderbra, with the company’s logo in the lower right corner. The poster, put up in Frankfurt tramway stations, was covered by a protective sheet of glass.

But the glass was made to look as if it had been cracked--cracked by the busty women in the ad as her Wonderbra lifted her so effectively that the glass couldn’t contain her or her assets.

The ad ran for 10 days at transit stations near shopping centers, as well as along routes that deliver passengers to the malls.