Apparently, the whole point of Karpas is to get the kids to ask about it. Yes, in the third Mah Nishtanah question. So the question is about the Karpas, and the Karpas is to provoke the question. Of course, we can't tell the kids that, so we tell them that the salt water represents the tears of Jews in Egypt- and who wants to eat salt water by itself? So we dip a vegetable in it! I am seriously dissapointed- this is quite a letdown.

While we're on the topic of disappointing facts about the seder, I should also mention that the purpose of Charoset is to kill a certain worm which lives in romaine lettuce, so that it doesn't make you sick.

Finally, an interesting fact. There is a halachah about the seder, which we mention during the seder itself: "Ain maftirin achar hapesach afikoman." Translated (somewhat): "We do not eat an afikoman after the pesach." This may seem a bit odd, since the very last thing we eat at the seder is the "afikoman!" And we know that nothing may be eaten after it!! On the one hand, it seems that the afikoman can NOT be eaten last, on the other, it MUST be eaten last! What's going on here?!

The answer is, simply, that "afikoman" means "dessert." So the halachah is actually that "No dessert may be eaten after the Korban Pesach." The "afikoman" that we eat today is zecher lapesach, in memory of the Korban Pesach, and that is why nothing may be eaten after it. The fact that we call it an "afikoman" is probably related to the halachah itself.

UPDATE: I have since learned that Charoset is also in memory of the mortar, as well as in memory of the apple trees.