When Lisa constructs her "Perky Patty's Princess Shop" the walls go diagonally. No LEGO blocks go that way.
While Bart is reconstructing the school/(s) there is a pink house behind him that changes in distance and appears on the other side of the road. This changes and then dissapears when all 12 schools are completed.
When Nelson is in pieces, he is seen with the standard legs but when skinner reassembles him, it changes to the short legs