Not really funny, but a similar famous person type story.
When I was in third grade I went to see the local high school's production of
Anything Goes. My eight year old self was star struck and my best friend and I went and got autographs from all the main cast. Years later, the
male lead went on to preform in several Broadway productions and now stars on the kids TV series
Hi-5. So I have a pre-fame autograph, haha. I mean, he's not famous enough for it to be worth anything, except maybe to him, but it was fun when I discovered that he actually became an actor.