Haha dude what?
I promise that I almost NEVER saw people wearing those clown costumes anywhere in Japan. Mayba, MAYBE, some folks wore them as part of the "Harajuku on a Sunday sit on the bridge and loiter all day in funny costumes that I never wear day to day" scene, but even then, most of those were gothic lolita. Its very likely that what these people are wearing are NOT day to day fashions, but instead are "freak you out" fashions they wear on Sundays. Mind you even then it seemed that most of the kids that did taht went to and from Harajuku/Meiji bridge area in rather normal clothes, towing a tiny little suitcase with their 'costume', which they changed into in a public toilet or friends van or some such.