At one time, when we didn’t dip the Karpas into the salt water. We dipped the Karpas into red vinegar or Charoses with red wine. To this day, some Jews, including Sefardim, still dip the Karpas into red vinegar or Charoses with red wine. The idea being that we dip the Karpas into blood. (Apparently, due to the blood libel accusations towards Jews, this minchag was changed.) More than this, Rashi, when discussing Yosef (37:3), defines Karpas as a “fine linen”. In other words, we start our seder in the same way that the Jews started their descension into Mitzrayim: by Yaakov giving Yosef a “fine linen” coat, Yosef’s brothers taking the coat and throwing Yosef into a pit, and Yosef’s brothers dipping this coat into blood and giving it to Yaakov.
During the Four Questions, we ask, On all other nights we do not dip even once, but on this night – twice. Dipping Yosef’s coat into blood (above) is the first dipping. The second dipping is the dipping into goat blood in order to place the blood onto the lintel and door posts so that the Angel of Death would passover the Jewish homes and not kill the first born. Yosef’s coat being dipped into blood is how yetzias Mitzrayim starts, dipping into blood in order to mark the lintel and door posts is how Mitzrayim ends. A critical part of the story of yetzias Mitzrayim is that we dip twice.
Yetzias Mitzrayim started because of the dysfunction between Yaakov, Rachel, and Leah, between Yaakov, Yosef, and his brothers. A critical aspect of the story of yetzias Mitzrayim is dysfunction and favoritism within a family. And, with this in mind, with this being clearly placed before us as a integral part of the seder, one of the first things we do is ask the youngest at the table to sing the Four Questions. Immediately afterwards, we discuss the four sons: the Chochom, the Rasha, the Tam, and the Sh’aynu Yodea Lish’ol. If the the fawning over the youngest child doesn’t bring out the dysfunction in a family, then the defining of each child as a Chochom, Rasha, Tam, or Sh’aynu Yodea Lish’ol will. Seemingly, the seder is a story about family dysfunction that attempts to integrate family dysfunction into the seder.