We already have a submission for best fan of the FIFA World Cup ... 'cause this one fits the bill!! The first day of the international soccer tournament kicked off on Thursday ... with Mexico and South Africa duking it out in Mexico City. There were plenty of memorable moments from the 2-0 win for El Tri ... but one clip of an adorable duck supporting its favorite team is taking the cake. A clip posted on social media shows the lil' one waddling among the humans in Mexico City ... all while