The Last Straw

When I went to McDonald's recently, I got this huge drink. It was awesome. I think it was 32 oz. Well, anyway, I reached for a straw, and there were only about 3 or 4 left, and I thought it was wierd. Then, a few minutes later, these two teenagers walked in. They ordered their food. One was kinda chubby, and had yellow plastic sunglasses for some reason. The other was tall, and wore the shirt of some band he likes. Then they went to get straws, and I heard one of them say "This is the last straw." I started laughing, and so did my mom. It just struck me funny for a bunch of reasons. One, that straw was really the last straw. Two, it would make sense if someone was mad because that was the last straw, so they would say "This is the last straw", and leave. And three, I don't think he realized what he said until a couple seconds after, and when something is funny, but isn't meant to be funny, it's normally funnier than when something funny is meant to be funny. Now the word funny seems like a funny word...