For me it was Jeff Kinney. I was meeting a different author I love, but there wasn't enough room downstairs and we had to go up. Turns out that's exactly where Jeff Kinney works! He's the author who got me into reading so I thought that was so cool
Gordie Howe babysat me often as a child. He was a neighbor and friends with my grandparents when I was young and would offer to watch me while my grandparents were busy. I had no clue who he was until many years later, still have the picture of me sitting on his lap.
I met Patrick Marleau a couple of years ago. He was on the Maple Leafs at the time, but just days after he was eliminated from the playoffs, I ran into him with one of his kids in San Jose. He was signing his kid up for hockey lessons at the local ice rink. Lo and behold, Marleau was back on the Sharks the next year.
I said hi to him and said I was a huge fan. He was doing his best to be nice, but he was 100% in dad mode, and his son was doing things he shouldn't in the store, so he had to keep scolding him. So I basically shook his hand and that was it. 😅