A traditional Irish dancer leaps during a St. Patrick's day parade on March 18, 2012 in London, England. Thousands of people lined the streets for the parade and a concert in Trafalgar Square. (Photo by Peter Macdiarmid/Getty Images)

Revelers cheer on the marchers during the 251st annual St. Patrick's Day Parade March 17, 2012 in New York City. The parade honors the patron saint of Ireland and was held for the first time in New York on March 17, 1762, 14 years before the signing of the Declaration of Independence. (Photo by Allison Joyce/Getty Images)

The Sydney Opera House is illuminated green on March 17, 2012 in Sydney, Australia. The Sydney Opera House joins Sky Tower in Auckland, and Table Mountain in South Africa in going green to celebrate St. Patrick's Day. (Photo by Brendon Thorne/Getty Images)

Onlookers watch the St. Patrick's Day parade on March 17, 2012 in Chicago, Illinois. Tens of thousands took advantage of record high temperatures and sunny weather to attend the city's annual St. Patrick's Day celebration. (Photo by Brian Kersey/Getty Images)

Members of the plumbers' union dye the Chicago River green for St. Patrick's Day on March 17, 2012 in Chicago, Illinois. The River was first dyed green in 1962 and has become a St. Patrick's Day tradition in Chicago. (Photo by Brian Kersey/Getty Images)

Catherine, Duchess of Cambridge presents shamrocks to members of the 1st Battalion Irish Guards at the St. Patrick's Day Parade at Mons Barracks on Saturday March 17, 2012 in Aldershot, England. 450 soldiers were on parade, accompanied by the regimental mascot Conmeal, an Irish wolfhound who received his own sprig of shamrock from the Duchess. This was her first solo military engagement and she will now inherit a tradition which begun in 1901 by Queen Alexandra and more recently carried out for 32 years by the Queen Mother. Prince William is honorary Colonel of the Irish Guards. (Photo by Paul Vicente – WPA Pool/Getty Images)