The safest way to remove dried egg from off a car with as minimal damage to the paint as possible is to just use water, car detergent and a microfiber or terry cloth. Raw egg is made up of proteins and fat, and a high alkaline cleaning agent will work well in breaking down the stain. However, a cleaning compound with a higher-than-neutral alkalinity will cause even more damage on a car's paint.
Egging is an annoying prank that has become a tradition in countries like the United States and the United Kingdom during the days leading up to Halloween. Apart from cars, houses and even people are egged, causing damage and injury and is considered a crime in some areas. The best way to deal with egg stains is to clean it off as soon as possible. Once the egg has dried up, it will be more difficult to get the egg out.
If the egg has dried on car paint, the best way to deal with the stain is to try to hydrate the stain as much as possible. One way to do this is to set the sprinkler on the stain directly for several hours. Once the stain has been sufficiently hydrated, use a car detergent along with a microfiber cloth or terry cloth to work on the stain.