Will Ferrell Crashes US World Cup Party -- 'I Will Bite Every German Player!'

The United States World Cup soccer team has a secret weapon ... and it's none other than RON F'N BURGUNDY!!!!!

Will Ferrell crashed the U.S. party in Recife, Brazil Wednesday night to rile up the fans before today's HUUUUUUGE match with Germany.

Ferrell was jokingly introduced as the team's newest player, where he promised the crowd he will take a bite out of each and every German player ... if that's what it takes to win.

Chew on that, Germany!