Create a new layer and name it Eyeball. Select Elliptical Marquee Tooland pressing SHIFT draw a circle. Inside Layer Effects make shadows as shown below:

Now create one more layer and name it Eye. Draw another circle inside and fill it with blue layer. Then apply Inner Glow filter. See the picture below:

Now create a new layer once again and name it Pupil. Draw one more circe inside (less radious). Now do one more layer called Reflection.  Select Elliptical Marquee Tool and draw ellipse? fill it with white:

Then you can add shapes of heads and etc.