Continuity mistake: After Tom flattens Jerry with the sign, Jerry runs on all fours backwards while flat and slides under the door of the Peter Peter Pumpkin Eater house. The close up of this shows that he does not pass by anything on the way and the ground is stone completely. The camera cuts to a wider shot as Tom dashes up and suddenly there is the statue of Peter with a sign that was not there when Jerry passed. Also grass appears in the area, and the stone ground becomes dirt.
Picture added by Quantom X