Has anybody ever seen this easter egg in FF IX? Apparently there's a "newly discovered side quest" that's been found thirteen years after the game's release. Here's a video of it in full:



and here's the conditions to unlock all the family members (Disk 4 spoilers) :
SPOILER!!:

Loading Disc 4.
The battle with Nova Dragon.
The fight with Maliris.
The flashback of Alexander.
The scene where Zidane talks to himself.
The flashback of Dagger on the boat.
The scene with the giant eye in the sky.
The battle with Tiamat.
The scene with the two planets colliding.
The scene where Quina thinks he/she is drowning.
The scene where Garland talks about memories.
The battle with Kraken.
The scene about Gaia's birth.
The battle with Lich.
The scene where Garland talks about the beginning and the Crystal.
The scene where the party enters the Crystal World.
The battle with Deathguise.


I've seen the part with Zenero and Benero talking, but never followed up with it...and apparently most haven't either until recently.

Source: After 13 Years a New Side Quest is Discovered in Final Fantasy IX