People fart in all kinds of different ways in this PSA, and while you might laugh, there's a serious underlying message.

The ad, by FCB Chicago, portrays little scenes in which unexpected people let some gas out. As well as the classic breaking wind in the elevator scenario, there's also nuns, ballet dancers and some corporate types gathering for a boardroom photo. To make it more amusing, each different scenario has a different sounding fart with its name -- the "rolling thunder," the "horn of Jericho," the "Spanish wind" and so on.

The spot, directed by Ben Flaherty with FCB Chicago's in-house studio, Lord and Thomas, is actually for Meredith's Miracles Colon Cancer Foundation and was made to highlight Colon Cancer Awareness Month (March). The foundation is acting on research that shows there has been a massive increase in the disease among people under 40, because they don't know the early warning signs -- like frequent gas.