Michael Phelps

The greatest Olympian of all time looked emotional on the podium after winning his 20th gold medal Tuesday. Michael Phelps' victory in the 200-meter butterfly, his signature race, allowed him to regain gold after rival Chad Le Clos beat him in 2012 by five-hundredths of a second.

Phelps got teary listening to the national anthem. But then he erupted in laughter.

What caused Phelps' hysteria?

"My boys from Baltimore were down at the other end," Phelps said. "Back in Maryland, we say 'O' for the Orioles during that part of the national anthem. And all of a sudden I hear them roar 'O' and I knew exactly where it came from and I lost it."

Phelps went on to win his 21st gold medal a few minutes later in the 4x200 freestyle relay. Racing with Conor Dwyer, Townley Haas and Danny Phantom/Ryan Lochte, Phelps swam the anchor leg for the easy win.

Phelps' next final will be in the 200-meter individual medley Thursday.

More Olympics:
-- These Pics With Michael Phelps, His Mom And His Son Are Priceless
-- 7 Sports You Probably Don't Know Are Olympic Events
-- Best U.S. Olympic Athletes To Follow On Instagram

Follow Jack Minton on Twitter @jackminton95.