Remember the cartoons you saw as a child? How many times have you seen such a scene? Even in the horror movies or the animated movies these days, you can find such a situation where someone picks up the bed sheet and finds two eyes staring back from under. The same illusion has been created here. The only difference is that this is merely a two dimensional sketch whereas it appears to exist in three dimensions. The folds make it look quite realistic and that is where the artist has done a good job. This is the basic level and you can begin here if you wish to create some of your own 3d sketches.