Misplaced shadow!

Well today while setting up my underwater world room I saw another glitch. While think of a place to put my dolphin toy, i picked it up with the curse. But when I saw to the right corner of the screen I saw a small shadow of something. I moved the dolphin and the shadow started moving too. In the image above i have marked the shadow with a red marking!
Even when I dropped the dolphin the shadow remained a few spaces away for the dolphin. HEHEHE it is pretty funny this is one Glitch i liked :D