Here are some of mine.
When you wake up and step into your cat's hairball he prob put there on purpose.
When you hold your snake and he poops on you.
When you take your dog out and he runs off while you are in boxers and don't have a choice but run after him.
When you finish cleaning your snake cage and as soon as he hits the new newspaper, he poops on it.
when your cat starts biting your feets at 3am.
Could go on and on...