Want to prank someone over breakfast? Well here is the ultimate practical joke. Follow along with this practical joke how-to video to learn how to write a secret ghost message on an egg that will appear on the inside of the egg after it has been boiled. All you need to write the ghost message on the inside of an egg is a 50/50 solution of vinegar and alum. Watch this video tutorial and see how it's done. Use this as inspiration for one of your April Fools Day pranks!