Usually part of initiations into a group of some sort. Commonly done by pooring nasty food over people, making them do humiliating things, and other ways.
The cops showed up right when we were done hazing the newbies with sardines, mustard, and marshmallows.
A small, square piece of absorbant paper usually containing one hit of LSD. Usually chewed and swallowed.
Let's buy a sheet of blotter.