I recall when the NL expanded in 1993 and created the Rockies and Marlins. It had been announced a couple of years before, and the idea intrigued me so much that my dad actually hunted down a Rockies' T-shirt for me in about 1991. The thing was pretty much worn out before the team played its first game. I guess the thing that captured my imagination was that there hadn't been any expansion since the '70s (the longest MLB had gone without expanding since they started expanding in the '60s), and that was before I was paying much attention to baseball.
(I also remember the FAN radio station broadcasting the expansion draft for the Rockies and Marlins. Dan Shulman was one of the guys doing commentary, and when Colorado drafted Kevin Reimer, Shulman said something like, “I don’t understand this at all. This is a National League team, and Reimer couldn’t catch the ball if you handed it to him.”)
Then I got over it.