The lovely Lucy Liu.
Small-Print Tutorial - the Making of a Caricature ActressThe first step is to find an image that you don't mind staring at for the next hour of your life.
Preferably one with a simple background that's easy to remove.
Clone the original picture (<Layer><Duplicate Layer> or Shift+Ctrl+D).
Add an alpha channel (<Layer><Transparency><Add Alpha Channel>).
Make sure the original image is invisible (click it's eyeball in the layer window). Back in the cloned layer, use the Fuzzy Select Tool, the Free Select Tool, the Eraser Toll and the delete key to clear away the background.
Use the free select tool to outline Lucy's head. <Edit><Cut> (Ctrl+X) and <Edit><Paste> (Ctrl+V) into a new transparent layer.
Use the scale tool (<Tools><Transform Tools><Scale> or Shift+T) to grow her head.
Use Free Select to copy bits of her hair and shoulder to fill the gaps. (I used separate Hair and Shoulder layers - that way you can move them from the back to the front of the stack of layers until you get the desired effect.)
In the head layer, I used Free select to copy each of her eyes in turn, and then scaled them up and moved them into place before pasting back onto her head.
For the final image, I messed about with colors and added a willow pattern background.
Try it yourself on a loved (or hated) one.