Juan Samuel

I met him at Jack Russell Memorial Stadium in Clearwater, Florida in 1996, when the Toronto Blue Jays came to play the Philadelphia Phillies in a spring training game.

Juan signed a 1990 Topps card #85.

http://www.baseball-reference.com/players/s/samueju01.shtml

Frank Robinson

I met him at Jack Russell Memorial Stadium in Clearwater, Florida in 1995, when the Baltimore Orioles came to play the Philadelphia Phillies in a spring training game.
After getting numerous Orioles players autographs before the game had started, I decided to head toward the Phillies side of the field. On my way, I see Frank Robinson sitting in the stands, signing autographs for a small group of people. Luckily I had a card of his on me, so I joined the group.

Frank signed a 1990 Topps card #381.

http://www.baseball-reference.com/players/r/robinfr02.shtml

Nick Leyva

I met him at a spring training game at Dunedin Stadium at Grant Field in Dunedin, Florida in 1994, when he was the third base coach for the Toronto Blue Jays.

Nick signed a 1990 Topps card #489.

http://www.baseball-reference.com/minors/player.cgi?id=leyva-001nic