Garland and the 4 Elemental Fiends is the best. Although I guess only the old school gamer would get that reference, And Ramah' story about Josef was also a favorite of mine. IX sure is filled with subtle nolstalgic easter eggs from past games.
Kain's Lance(Kain the Dragoon from FF IV)
Ramuh's Story about Josef(Josef from FF II)
Magical Fingertip(Artifact that talks about Gogo from FF V and VI)
Garland, the 4 Elemental Fiends, and the Rat's tail(All from FF I)
Freya's Dragon ability "Reis's Wind"(Reis the Dragoneer from FFT)
The Cloud and Squall line(Cloud FF VII, Squall FF VIII
Garnet's real name(also from FF I)
Doga's artifact and Une's Mirror(FF III)
Others that I haven't mentioned or completely forgot about
Garland and the 4 Elemental Fiends is the best. Although I guess only the old school gamer would get that reference, And Ramah' story about Josef was also a favorite of mine. IX sure is filled with subtle nolstalgic easter eggs from past games.