1. Watch the Family Guy episode where Peter invites his boss Mr Weed round for dinner who then dies choking on a dinner roll.

2. After Mr Weed's death the Superman actress Margot Kidder appears and then breaks through the window completely shattering it.

3. In the very next frame though we can see the window fully back to it's unbroken state.

Not a major slip up but so blatent that it is worth pointing out.