Happy slap

From Frikipedia

The slightly dark craze sweeping England. Involves bunches of teenagers walking round towns, violently assaulting someone and filming it on their mobile phones.

The craze was of fairly limited appeal, until Tonight With Trevor McDonald and the Daily Mail suddenly publicised it like crazy in a fear lavished theatrical manner. Since then, 99% of all teenagers perform a happy slap at least once an hour. According to the Mail.