Cascarones are eggshells that have been hollowed, painted or dyed, filled, then resealed. Traditional fillings include perfume, confetti, sage, and lavender.
To make your own:
One dozen eggs
acrylic craft paint and brushes (using a sponge also gives the egg a really cool look)
clear carton sealing tape
whatever you want to fill your egg with
Make a small hole in both ends of the egg-be careful not to crack the rest of the egg. Holding the egg over a bowl, gently blow on the larger end of the egg and push out the yolk and whites. Rinse, then replace in the carton to dry overnight. Carefully paint and decorate them. Tape up the bottom hole with clear tape. Carefully fill the shells, then seal the top hole.
Tradition says that cascarones were brought out on Easter morning, when the object was to surprise your loved ones ad hit them over the head with an egg.
From: "Sabbats: A Witch's Approach to Living the Old Ways" by Edain McCoy (pg. 112)