Getting permanent pen ink on a favorite white shoe just might spell the end for that particular pair, but don't lose hope right away. Try these stain-removal techniques to take the stain out of the shoe, or at least lighten it to such a degree that it is still wearable. Using household products, you can get to the stain quickly, improving your chances that you can remove it.
Apply rubbing alcohol or water-based hairspray lightly to the stain, then blot with a white cloth. You will see the marker ink transfer to the cloth. Continue to apply either the alcohol or the hairspray and then blot. When the stain is gone, apply clean water and then blot.
Pre-treat the stain with a strong liquid detergent, then soak the shoe in a solution of bleach and water (one part bleach to five parts water) for 15 minutes. Attempt this step only if the spot treatment did not work and you are willing to risk damage to the shoe.
Take the shoe to a professional dry cleaner if you are unable to remove or lighten the stain effectively. The dry cleaner may have tips or products to help.