When Homer and Bart are tethered together and Bart has to bring Homer to school with him, Mrs. Krabappel tells Homer to try and sleep. Homer begins to snore loudly and Bart shoves a blue and white shoe in Homer's mouth. In the next scene, we see that the shoe has changed from blue and white to solid gray.
When Homer and Marge are putting up the 'Big Meanie' sign on the Judge's home, Homer hammers 2 nails in next to each other, revealing the letters "B" then "I" for each nail. In the next shot, the sign only has one nail on each end and does not fold in at the middle as the previous shot showed.