Square One TV had a brilliant take on this. One of their cast (of the main show, not Mathnet) would say something like: "I've thought of the biggest number: 973,281,472!" At which point the rest of the cast would respond (exasperatedly, in unison): "Add one more to it!" Really drove home the point that no matter how big a number you thought of, you could always produce a bigger number by adding one to it.