A student told me today that her father used to wake her in the morning by pouring water on her and shouting "Śmigus-Dyngus!" He said that it was a Polish tradition.
While I am of Polish heritage (I'm basically half Polish, a quarter Irish, and a quarter French. I usually just claim that I'm Irish), I had never heard of such a thing.
So, I took a look around the web for the potential origin of such a practice, and it turns out that today is Śmigus-Dyngus or "Wet Monday," a day celebrated in Poland and in some communities of Polish Americans on the first Monday following Easter. According to Wikipedia, the important traditions of Wet Monday are celebrated through the following festive activities:
Traditionally, boys throw water over girls and spank them with pussy willow branches on Easter Monday, and girls do the same to boys on Easter Tuesday. This is accompanied by a number of other rituals, such as making verse declarations and holding door-to-door processions, in some regions involving boys dressed as bears.
So, if you'll excuse me, I need to go and prepare my bear costume for today's celebration. A merry Wet Monday to all and to all a good night.