I liked seeing all the allusions to previous game's as I was playing through and it was great to see a character named Garland as the hand behind the scenes. There was a fact on that allusion page that said:

Garland shares his name with a character from the original game. The character Mikoto even goes so far as to mention later that, "Garland once tried to take control of the cycle of souls by force, but failed," the strongest evidence suggesting that perhaps the world of Final Fantasy IX is in direct relation to the events of the first game in the series.
That is a very interesting point and could absolutely make sense, like Garland has created another world where he obviously would take a different form and is once again trying to take control of the cycle of souls. As far as Zidane being too cheery, which is totally off topic, I have to disagree. I think Zidane as a character evolved very nicely from start to finish, beginning as a thief who was just worried about living in the now and making the most of it, and of course girls, to getting a larger perspective on what he should be thankful for, understanding who he is, and knowing that he could stand with his friends and count on them to make it through any troubles. He is my favorite character so I may be biased a little =p