Jara Cimrman (also known as Jara da Cimrman), the greatest Czech ever known, was an inventor, playwright, teacher, composer, criminologist, and philosopher (among other things). Born in Vienna, Austria (the exact year is lost in the history), he was an important figure of late Habsburg period, albeit mostly overlooked by his contemporaries.
He invented telephone, but was beaten to the patent office by Bell, discovered Yetti (which he named Ja-ty), brought rabbits to Australia, and wrote a plethora of plays.
Most of his work has been re-discovered in the second half of 20th century randomly during renovations of a house in a town he spent most of his life. Researchers, called cimrmanologists, have spent years going through his notes to understand his genius and now try to educate the public on this great polymath - largely through lectures (and playing his plays) in Cimrman's theatre. (These plays and lectures (in Czech language) can be seen on YouTube)
Unfortunately, he's virtually unknown outside of Czechoslovakia. However, in Czech Republic he won popularity contest of most beloved Czech in the history (Poll by Czech TV in 2005). Oh, and he's also completely fictional.