In "The Thing & I", when Bart pulls up his shirt and discovers his scar on his right side, the next shot from behind shows him looking at his left side.
When Bill Clinton and Bob Dole are in the glass tubes the height of the metal rings on the tubes changes in different views. From the front they are high enough to cover their groin areas but from behind they are low enough to show their buttocks.
When Lisa is shrunk down and teleported into the petri dish, she has her bedroom slippers on. The next time we see her feet they are bare and she demands that someone bring her shoes (she had time to remove the slippers, but no reason to.)
Bill Clinton is kidnapped from his bed in the middle of the night. He is clearly seen wearing pajamas. Yet, after the aliens bio-duplicate into Dole and Clinton, both are dressed in suits.
One of the aliens, disguised as Bob Dole, asks the people to vote for him but doesn't know Bob Dole's name, so he looks at the campaign button on the suit shirt. However, the button only has the last name on it.