(A very angry customer storms up to the counter at the party shop I was working at.)

Customer: “These balloons are no good! I spent all afternoon blowing them up, and none of them will float!”

Me: “What did you fill them with?”

Customer: “What do you mean? I just blew them up, and none of them will float.”

Me: “Did you fill them with air or helium?”

Customer: “Air.”

Me: “They won’t float unless you use a helium tank.”

Customer: “NO! Look, it says on the packet, ‘Helium Balloons’.”

Me: “…”