When Burns and Smithers are driving away, Burns is shown answering the phone. Later in the same episode, it shows that he never does that himself.
When Burns sits back down after making his failed phone call to Smithers, his black eye disappears.
If Burns were really 104 years old, he would have been born long after the dodo became extinct.
Lisa is eating spaghetti and meatballs with the rest of the family in the first scene of the third act. This is a few episodes after she had officially turned vegetarian on Lisa the Vegetarian. Lisa's vegetarianism wasn't mentioned again until Homer's Phobia, so it may not have been considered to be canonical yet.
When Smithers calls Homer, his phone is black, but in another scene it's blue.