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George Washington - The first leader of the United States of America was a mule breeder in his spare time.

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George Washington - After seeing how effective they were in Spain as pack animals, he had them imported and started a mule-breeding frenzy among the townspeople of Mount Vernon. 

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Thomas Jefferson - When he wasn't leading his people through the Revolutionary War, he invented spy gadgets. 

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Thomas Jefferson -

His most famous invention was the "wheel cipher," a contraption used to decipher coded messages.

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Abraham Lincoln - In addition to leading the country through the Civil War and abolishing slavery, the 16th president liked to wrestle.

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Abraham Lincoln - At one point he was the wrestling champion of his county in Illinois. His wrestling background even came up during his presidential campaign, adding to the image of him as a strong and determined leader.

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Bill Clinton -

The 42nd US President had an ear for music and played the saxophone.

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Bill Clinton - During his candidacy, the media called him the "Elvis candidate," but it didn't deter voters from electing him as their president. 

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Calvin Coolidge - President Coolidge had a love for horseback riding, but developed an allergy later in life and was unable to continue riding.

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Calvin Coolidge - He received a mechanical horse as a joke gift and ended up loving it and riding it regularly. 

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Franklin D. Roosevelt - Our 32nd president had a penchant for detective stories. 

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Franklin D. Roosevelt - He even ended up helping write a mystery novel, called 'The President’s Mystery Plot.'

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George W. Bush - The 43rd president participated in many other activities in addition to running the country. He was a businessman, managed the Texas Rangers, and was in the Texas Air National Guard. 

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George W. Bush - However his real passion was painting, and he loved creating portraits of dogs more than anything else.

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John Quincy Adams - The son of a Founding Father and the sixth president of the United States enjoyed skinny dipping.

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John Quincy Adams - He allegedly swam naked in the Potomac River every morning at 5 am. 

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Lyndon B. Johnson - The president used to take guests on joyrides around his ranch in his amphibious car.

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Lyndon B. Johnson -

His morbid pastime included pretending to lose control of the car and driving unsuspecting guests into a lake. 

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Theodore Roosevelt - Teddy Roosevelt was a huge fan of boxing after taking wrestling lessons from a middleweight boxing champion.

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Theodore Roosevelt - He continued boxing even after elected as president, until an artillery captain permanently damaged his eye.

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Theodore Roosevelt - Another one of Roosevelt's hobbies was hunting.

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Theodore Roosevelt - While not necessarily a strange hobby in and of itself, he took his passion to such an extent that he ended up killing over 11,000 animals during a single safari through Africa.

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Andrew Johnson - Lincoln's successor enjoyed making his own clothes during his free time.

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Andrew Johnson - Prior to his presidency, he spent years working as a tailor. Apparently, old habits do die hard.

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Millard Fillmore - The president had an insatiable apettite for reading.

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Millard Fillmore - He reportedly raced across town and risked his life to fight a fire at the Library of Congress in 1851.

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Barack Obama - Barack Obama is an avid comic book collector.

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Barack Obama -

He has even been featured in many comics, including the 'Amazing Spider-Man #583' pictured above.

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Richard Nixon - The 37th president had an infamous reputation for being the best bluffer in the US Navy during World War I.

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Richard Nixon -

He loved a good card game, and won so much money gambling that he used his earnings to fund his campaign for the US House of Representatives in 1946.

See also: Surprising facts about the US presidents

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