If your little one has decided to decorate the walls with non-washable crayons, there is an alternative to using a magic eraser, and it is much cheaper too! And your walls will look good as new when you are done.
Simply get a washcloth or kitchen towel damp, then add a small amount of toothpaste. Gently scrub the wall with the toothpaste, then use a clean damp cloth to wipe off the toothpaste. The crayon should be removed. If the color is especially dark, or your child used some elbow grease when coloring, repeat if needed.
If there is a large area needed, it might be worthwhile to buy inexpensive dollar store toothpaste to do the job, especially if you use a more expensive whitening or complete style toothpaste.
A day or so later, if the wall has a “chalky” or “flat” look to it, just wipe it down again with a damp washcloth to remove the last traces of toothpaste.