Last night on the Late Show, Reese Witherspoon explained to David Letterman that when she was in Paris with her kids, she took her daughter to the Eiffel Tower and the Musée D'Orsay, but her son really wanted to visit the sewer system. Reese claimed she was "very busy working" and couldn't take her son to the sewer, so she had her assistant go with him. David Letterman was curious as to why a Parisian sewer would be cooler than any others; Reese answered, "It's French!" Clip above.