This is a true story .
It happened to me over 30 years ago.
I was in Chicago working for a company that sold hospital equipment and supplies. I took off an afternoon and went to Chicago planetarium to view a show. I watched the show and afterwards went out into a park like area around the planetarium. I was sitting by a tree when all of a sudden a young man popped in.
By popped in , I mean , he wasn't there one minute and the next minute he was there. I had had experiences in the past where things just "popped in" , so I wasn't greatly alarmed. I ignored the young man hoping that he would just "pop out" and be gone. Years before one time I was riding on a bus when a little boy popped in through the front of the bus wearing an outfit from the 19th century and pulling a wheeled toy (he kept walking through the bus and walked out the back - I don't think anyone else saw him.
Back to story at hand - this young man had just "popped in" and was sitting close to me by the tree. I ignored him for a few minutes hoping he would go away. After a few minutes when he didn't go away I said "hello". He looked at me and said "I thought for a while you weren't going to say hello" He asked me what I was doing and I told him I was at the planetarium watching a show. We talked for a little while. Momentarily something in the distance caught my eye, when I turned back to the young man he was gone.
Only now while writing this do I think that this young man looked a bit like the little boy who walked through the busy, but memory is known to play tricks.
At any rate, the young man was gone. I marked it down as another incident in my life that would be hard to explain.
At least a year or so later I was in Tennessee helping some friends to move. I was in a friends SUV going up a road when we passed by a person who looked like the young man I had seen in Chicago. I told my friend to back up. We backed up to the young man and it was the same young man I had seen in Chicago. We exchanged greetings. I asked where he was going and he said right up the road and he asked for a ride which we provided. I asked him what he was doing in Tennessee and he replied that he could be anywhere he wanted to be. It wasn't a long way to where he was going and soon he was getting out. I asked him if I would see him again and he looked at me and said "I honestly don't know". I told him to take care and he told me the same. I haven't see him since then.
This was a friend that I met in "real" or waking life (if there is such a thing and such a difference). I have had other friends over the years who only come and visit in dreams.
I have no idea who or what he was , but we were friends.
In the years since, I haven't had anyone else, just "pop" in, but if it happened today, I might not wait quite so long to say hello.