Then turns he's just in a coma for 20 years and he as ghost thought he was dead, the grave he was (supposedly) narrating from, is actually a grave of someone with similar name who have died in the same day.

And after he wakes up he won't believe it until he checks that grave and discover how the name is different, everyone have a good laugh until someone says "But how did you know about this grave when you were in the coma?"

And the narrator freaks out about his whole ghost thing!!

How about above for a twist?