When you are trying to tell a legit story one on one, but it might sound perverted or disgusting if other people hear it.
The person listening can't hear you, or doesn't understand it at first, so you yell. Simultaneously, the entire room gets quiet.
You end up embarrassed and a wierdo for several minutes.
Matt: "What? I couldn't hear that last part, say it one more time."
Scott: "I said, I stuck it in the hole crooked, so she didn't give my money back!"
Matt: "Owch man, total schoolbus scenario, sorry."