Nicki used to be a waitress and was always getting ink stains on her uniforms. She found that it came right out with nail polish remover.
Now the problem with this suggestion is that since Nicki quit being a waitress, they began to produce a variety of nail polish removers, some specifically with and some specifically without acetone, and it was the acetone that was doing the job. So we tested a few things.
Neither the "without acetone" nor the "with acetone" polish removers did much good on felt pen marks -- although you can have some success with lighter fluid on that.
For ball point pens, the ?with acetone? remover did wonders, just as Nicki said, but the "without acetone" remover didn't do much.
With all of these chemicals you have to check if they will damage the clothing itself. (Test it first on an area that won?t show, like inside a seam.) There are specific warnings about some materials right on the nail polish remover bottles.