An overhead shot of the Simpsons house exploding shows one of the second floor windows shifted further away from the other one.
The veterinarian offers to spay Homer; this is incorrect since spay is the removal of the ovaries and/or uterus in a female animal. The correct medical term is "neuter".
Mr. Burns is shown time and time again, season after season, being unable to remember Homer's name or the things Homer and his family have done that impacted his life, yet he comes to the hospital and wants to pull the plug on Homer, telling Marge that she has no idea "what this man has put me through", which is followed by a clip. So this time he remembers Homer, even though he doesn't speak his name.