Whaam! Varoom! R-rrring-g! The canvases of painter Roy Lichtenstein look as if they're lifted from the pages of comic books. Comics were a big inspiration for this pop artist, who was rich and famous when died in 1997 at age 73. But at a major Lichtenstein retrospective at Washington's National Gallery of Art, you can see that the artist found inspiration beyond comic books; he also paid his respects to the masters — Picasso, Monet and more.