I'm starting off with the 1989 Topps Major League Debut set. This was a new concept for Topps starting in late 1989 where they created a card for each player who made their debut in MLB during the 1989 season. Obviously, this was an idea to create lots and lots of rookie cards. Overall, it didn't really catch on, because although there are some superstar players in this set, people don't generally care about these cards all that much or regard them as the true rookie card. For example, Ken Griffey Jr. has a card in this set, but any collector will tell you that his Topps rookie card is the 1989 Topps Traded card, which came out earlier than his card from the ML Debut set.
Anyway, here is a shot of the box:
Holy amazing Technicolor®, Batman!
Right away, there is some confusion about this set. It's called a 1989 set, and the copyright date on the bottom of the box is 1989, but it uses the 1990 Topps set design, as you'll see soon enough. In Beckett, I believe it's called 1990 Topps ML Debut. If I remember correctly, this set did actually come out before the base 1990 set, and the 1989 really refers to the year in which all the players debuted.