Look down. 

Actually before we start, this is only relevant to males... sorry.

Look down.

What are you wearing? I don't want to sound too crude, but, what underwear are you wearing?

There's a strong chance it's boxer shorts.

Now watch this

In 1984 UK men didn't really think much about what underwear they wore. In fact if you look at many pictures from the time you'd be correct in thinking they didn't think much about their outerwear too.

Briefs though were common.

When the BBH creatives came up with this ad to promote Levis shrink fit 501's, the script originally had Nick Kamen wearing briefs. When the producers sent the idea to the Advertising Standards Authority they took exception. They didn't feel briefs left much to the imagination. The ASA suggested a compromise, they said they'd be fine if he wore boxer shorts.

BOXER SHORTS!

This was 1984. In the early 80's boxer shorts were what middle aged American men wore. It was a daggy throwback to the 1950's. However they still wanted to make the ad and Nick was a good looking guy, so it could still work, and so it was made.

Many Levis were sold.

And many boxer shorts too.

Unexpectedly Boxer shorts were now seen as sexy. Men could now pose semi naked without the unfortunate budgie smuggler look... if they were so inclined. Boxer shorts infiltrated British media and culture. Eastenders characters were caught-in-the-act in boxer shorts, Matt Goss from Bros. appeared on stage in just his American flag boxers and more relevant if you're a guy, you're probably wearing them now.

Fashion changed just by an ad and it wasn't even trying to sell them.

Advertising is pervasive. Sometimes it mimics culture and sometimes it changes it.