Seriously. Just don't shoot it.
http://www.rrrrthats5rs.com/games/dont-shoot-the-puppy/
Noooooooooooooooooooooooooooooooooooooooooooooooo!
Poor puppy. I managed not to shoot it until the end (there are 15 levels).
yay, it works now
hehe
You just have to not shoot the puppy.
(Hint: It's to do with moving the mouse)