67-year-old David Letterman challenged Serena Williams to a tennis game outside the Ed Sullivan Theatre in New York before The Late Show.
Despite her high heels, Serena got so into the show game with her powerful strokes that one of her balls flew off the court and broke the window of the nearby Hello Deli.
After their knock-about, the 67-year-old gallantly kissed the tennis champ's hand before they walked into the theatre. More photos below...