Perspective

Then for reference, these are the sort of eyes I can draw nowadays. I used to be terrible at faces and expression so it's an important field for me. Also when I started drawing the mouths at the top I realized they made faces all by themselves. I've experimented with perspective a little more since then.

For example the 3nd face down from the top on the left, which can be seen as a smiling face pressing against something or a frowning face with a nose (or something else I haven't considered).