Most animals contract and dilate their pupils depending on the light available around them. Geckos are no exception but unlike other species the difference between those two stages are much more dramatic. They go from having cute round pupils in low light to evil narrow slits when it's too bright.
It's true! In fact, you have more than fifty sphincters in your entire body, and most of them have nothing to do with controlling your bowel movements.
Pixiq has a great write up on the similarities and differences between the human eye and a camera. Apparently, we're the same in image focusing and light adjustment but different in lens focus and sensitivity to light. What else?