People are different in many ways. One of those is the way they fart. The Walking Farts describes somebody that lets their farts out in small, easy to handle squeezes, if done whilst walking, this makes a familiar "Pop!... Pop!... Pop!... Pop!" noise. The walking farts generally do not smell as much because they let out smaller doses of Methane, thus this is the prefered way to fart
Did you hear Tom walk by? He must have the walking farts!