This happen to me once when I was a young kid walking home from school.

There were two other guys with me, older than me. They were talking to each other about programming languages. I have been programming from a very young age so I knew a lot about programming and I knew a few languages back then, but they were taking about Java, a language which I wasn't into yet back then, so I just listened for a while to what they had to say.

The first guy told the other, "You know I'm great at Java." The other guy responded "I can do anything in Java." Then I said as a joke "Oh, can you do hello world?". The guy said "Hello what? What do you mean?" The other guy said. "Is that a retro game?" I just laughed. Then I told them to go learn how to output text in Java.

A bit of current history about these guys:
The first now works in C# for a quiz test company, he never learned Java or languages other than C#. The second one owns and works at a scrapyard. They are both great guys, but they like to brag.