How do you remove nail polish stains so your parents won't notice?

It depends on what item the nail polish is staining. It is nearly impossible to remove nail polish from fabrics/carpet/tablecloths because the nail polish remover will bleach and damage the fabric before it will remove all the color of the polish. Commercial stain remover products will not be effective on nail polish as it is paint based.

If it was spilled on glass then it is safe to use nail polish remover. On wood furniture it will also remove the varnish and wood stain along with the polish so that isn't good either. In other Words, your parents are going to "notice" wherever you spilled the polish.