Michael Phelps laughs during medal ceremony; find out what caused chuckle

RIO DE JANEIRO, BRAZIL - AUGUST 09: Gold medalist Michael Phelps poses as bronze medalist Tamas Kenderesi of Hungary look on during the medal ceremony for the Men's 200m Butterfly Final on Day 4 of the Rio 2016 Olympic Games at the Olympic Aquatics Stadium on August 9, 2016 in Rio de Janeiro, Brazil. (Photo by Pascal Le Segretain/Getty Images)

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RIO DE JANEIRO, BRAZIL - AUGUST 09: Gold medalist Michael Phelps poses as bronze medalist Tamas Kenderesi of Hungary look on during the medal ceremony for the Men's 200m Butterfly Final on Day 4 of the Rio 2016 Olympic Games at the Olympic Aquatics Stadium on August 9, 2016 in Rio de Janeiro, Brazil. (Photo by Pascal Le Segretain/Getty Images)

Hitting the Olympic medal stand for some is a once-in-a-lifetime moment; for others it has become old hat.

Swimmer Michael Phelps experienced a bit of levity Tuesday night while receiving another medal, WRC reported.

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He started to laugh during "The Star-Spangled Banner."

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When the song got to the line "O say does that star-spangled banner yet wave," the crowd yelled, "O!"

You can watch the video here.

The shoutout during the national anthem was a tradition started in Baltimore at Orioles games. The Orioles are also known as the O's. Phelps originally is from Baltimore, Maryland.

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Phelps was on the dais for winning gold in the 200-meter butterfly, beating Chad le Clos. He racked up his 20th and 21st gold medals Tuesday night.