I really enjoy working with Alan, I like the way his mind works and his BRILLIANT REAL WORD MAGIC.
A card is selected from a regular deck. The card is held face down. A Sharpie is shown as you claim usually I would ask you to sign the card. However, 

today we will try something very unusual. You strike the face of the card with the pen. Instantly the Sharpie logo vanishes and the INDEX of the card appears 

on the Sharpie. This looks GREAT. The Sharpie logo MUST go somewhere. The card is turned over and the LOGO is now on the playing card.
A fun, super easy to do card effect, that you can carry anywhere and perform at the drop of a hat.