No one wants to come out and find that their car has been egged. Egg can easily damage paint if left to dry, and egg shells can scratch the paint's clear coat upon impact. But with a few simple household items you can remove egg and prevent permanent damage to your car's finish.
Remove as much of the egg as you can with a water hose. This usually works well for egg that has not dried and stuck to the surface of your car.
Fill a bucket with two cups of water and two cups of vinegar. Soak the wash rag in this mixture and apply it to the egg stain.
Leave the towel on the stain for 15 minutes. It may take repeating to soften dried egg yolk, but in the meantime the vinegar will neutralise the egg's acid and keep it from further damaging your paint.
Rub the stain off of your car with the wash rag. Wash your car, if possible, and wax as usual.
If the paint on your car has been blistered or cracked by the egg, you will have to consult a professional for repainting. If it is slightly discoloured, then you can disguise it by using a clay bar. The best colours for this option are beige, white or silver.