What artist is known for his melting clocks painting 'The Persistence of Memory'?

Salvador Dalí

Which twins, children of Zeus and Leda, are known together as the Dioscuri? What river in the Greek underworld was associated with forgetfulness? What's the most common distance of a triathlon 'Olympic distance' race in kilometers? Who portrayed Princess Leia? Who was famously known as "The Great Commoner" due to his appeal to ordinary citizens in 19th-century America?