> Perfect strangers (or so I think) come up to me in the halls and say "Hi (my name goes here, it's not jimmy and i would like to keep it a mystery for a while)!" and i say, "uh... Johnny!" I said this to 5 people yesterday and they walked away laughing...

There's nothing wrong with you. You're just the victim of a practical joke.

True story:

In college, I thought it would be fun to pass a stranger and say, enthusiastically, "Hey!! How ya doin'? It's been a long time!" Well, once, when I was in a rambunctious enough mood, I did.

And he said, "Yeah, I guess it has, hasn't it?"

It turned out I did, in fact, know the guy, but I didn't have a clue when or where I met him. In the ensuing conversation, I discovered he had been a member of my study group for an introductory psychology course I took my first year.