The burger chain, no doubt expecting an early exit for South Korea, printed many times more cards for Korea than it did for Brazil or Germany. Now with Korea just one game away form the World Cup finals, McDonald's could have to pay out hundreds of thousands of pounds in prizes.
The competition, which kicked off on May 15, was open to anyone buying large or super-size fries in any participating McDonald's restaurant.
Customers were given a referee's red card, which had printed on it the name of one of the qualifying teams.
If the country printed on the front wins the 2002 World Cup then customers can claim the prize highlighted below the country's name. This could be either £50 or a five-star holiday for four people.
If Korea beats Germany today, it will find itself in the World Cup final and McDonald's could find itself paying out to many more thousands of customers than it had anticipated.
The promotion was supported with marketing and ads by Leo Burnett starring Teddy Sheringham and Rio Ferdinand.
McDonald's is one of the official sponsors of the Korea/Japan 2002 Fifa World Cup and has promoted its link with the tournament heavily.
As well as the Red Hot promotion, McDonald's signed up 1966 England World Cup hero Sir Geoff Hurst and Manchester United coach Eric Harrison to head up its grassroots football programme.
According to Korea's profile on the McDonald's Redhotfootball.co.uk website: "Once at the finals their record is not so good: they have never won a match".
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