As I write this, people around the world are painting their faces, their cars, their dogs. They’re getting tattoos and buying funny hats. They’re tearing up flags and sewing them into ponchos and dresses and pants.

A virus? An epidemic? No, it’s just the FIFA World Cup 2010, which literally kicked off this morning. And futbal fans everywhere are asking the same question: where can I find World Cup underwear?

Glad you asked. We’ve already written about the World Cup limited edition swimwear lines from brands like Etam and Parah. But what about the guys? Any true World Cup fan is going to want to show off his team colors any way he can — and that means skivvies, too.

Special edition World Cup men’s underwear collections are available from a handful of labels in the U.S. (alas, the Europeans take this stuff way more seriously than we do). You can take your chances by trying to find World Cup underwear at retail outlets, but those chances get slimmer with each passing day.

Best bet? Get your favorite team colors in men’s underwear by buying online and shipping overnight. Here are some choices available NOW:

CALVIN KLEIN UNDERWEAR — CKU was a late entrant into the World Cup underwear market, but the Calvin Klein X Global Trunk collection of flag-colored boxers is a must-have. Buy through Skiviez for best results. On sale for $21 a pair.

DOLCE & GABBANA — D&G produces a line of flag-colored briefs and boxers. The selection is limited, though, and every pair is emblazoned with the D&G brand lettering. Yuck. Still, if you must-have these ($19-21) check out the D&G online store.

GIGO UNDERWEAR — Gigo is a Colombian label which, to our eyes, has the best collection of World Cup men’s underwear. Better still, you can get Gigo in the U.S. by ordering through Underwear Station.

AUSSIEBUM — Aussies take their undies seriously, and their football. By now, almost every guy in the Outback is wearing Aussiebum’s hilarious cartoon boxers called The Game (see top picture above), which salutes the worldwide obsession with soccer.

If you want to be part of the action, but not too partisan, this is your pick. $12 at Aussiebum.com