Check out my buddy Mr. Squirrel.
Each photo will gets closer and closer. The first one is zoomed all the way out. The last he is right up against my lens.. you can count every whisker.
I saw him about 75 feet away and chirped at him. It took me about 30 minutes but every time I made a chirping noise he came closer and closer. Finally when he was about 4 feet away I couldn't get him in my lens any more.. he was to close. This was way out in the woods, not even close to any houses so I am sure he wasn't used to people.. just very friendly. I finally had to stand up cause I thought in another couple of minutes he would be in my lap. Zoom in on the last pictures squirrel and you will realize just how close I got to him (or him to me).