This slip up occurs in episode "Sold-Y Locks". In the scene where Robert Goulet takes Doug and Deacon to his dressing room and to find a wig for Carrie, Doug draws a face on the mannequin head the wig's on, to see what it would look like on her. Here's where they slipped up, when Doug draws the face, you clearly see that he used one black Sharpie marker, but when they show the face, the lips are a vibrant red. How could this be?