Anyone who has kids knows how frustrating when they get to that stage where they start thinking its okay to use your walls as their own personal coloring book. But don't fret, because the solution is sitting right in your fridge.
Mayonnaise is one of the best ways to wipe off crayon scribbles. The secret here is the oils in the mayo, which help by breaking down the wax in crayon. Just dab a little over the crayon lines, let is sit for a few minutes before getting to work with a damp cloth. Just apply a little pressure, and both the mayo and the crayon should both come off in one fell swipe.
Other methods you can use includes a dish sponge soaked in vinegar to rub the marks off without destroying the paint underneath, or even a piece of bread rolled it into a tight ball.