My first thought is to show them pictures of the event. This is actually misleading as it doesn't express the feeling of Burning Man. Spending days in the desert with music thumping from different directions 24 hours a day, extreme temperatures and camping living conditions does not get translated into pictures. What does come across is the eclectic mix of people. . . Possibly for the first time in their lives.
Some people are merely out to draw attention to themselves. . . to outdo the next guy in oddity.
Some people are out to bolster their self-image by helping others, using a contraption they've been developing for months before the event. And the rest of us are there to witness it all. People waited in line to be the horse for this buggy. The Tesla Coil can be seen in the background. We've all seen the typical American male with the beer belly gut.