During Grandparents' Day, as Mrs. Krabappel invites Grampa to speak, he's holding his oatmeal spoon in his left hand. Before and after, he's holding it in his right. When Grampa starts to sit at Mrs. Krabappel's desk, and during his nonsensical stories, the spoon has vanished.
Although Grampa's military unit was known as the "Flying Hellfish", both the elaborate headstone and stationery letterhead read "Fighting Hellfish."
Mr. Burns is shown to have the strength to kick Bart halfway across his and Grampa's boat. This is inconsistent with his appearances in other episodes, where he is extremely weak and tires easily, though he could have summed up all his energy just to do that.