In an episode of Tom & Jerry where they're attacking each other with fireworks, Tom is killed in a firework explosion that creates the 48 star U.S. flag, which Jerry salutes. He sends a letter, asking to send more cats. JOKE: Jerry has been on a cat-killing spree. Whenever he kills another cat, another star is added to the U.S. flag. Every time that happens, Jerry watches the [new flag] firework explosion, saluting the new U.S. flag. So that's 48 cats killed, now ready to add a 49th star. USA! The 13 stripes represent the first 13 cats Jerry killed & did so all at once. A real killer, amirite?