Instructions 3D Viewing
Lean back and cross your eyes so that they see four total images instead of the normal two.
Then they slowly uncross your eyes until two out of the four images overlap each other.
Once the middle two images are perfectly aligned you start to see a single 3D image in the center. Other people get close to the screen and let their eyes lose their focus and their brain just does the rest.
NOTE: Want to make a stereoscopic comic like this? I wrote a blog post explaining how.