i went to this webby site and found some interesting things.
these are how to unlock them

Ashee (XII) Complete Second Sphere Tournament
Chocobo (FF) Complete Fourth Sphere Tournament
DQ2 Main Character Complete Third Sphere Tournament
DQ5 Main Character Complete First Sphere Tournament
DQ6 Main Character Complete Third Sphere Tournament
DQ7 Main Character Complete First Sphere Tournament
TaruTaru (FFXI) Complete Fourth Sphere Tournament
Vaan (XII) Complete Second Sphere Tournament
Auron FFX finishing fourth tournment mode
Dragon Lord DQ finishing third tournment mode
Kukuru (Kukule) DQVIII complete the first tournament
Moogle FFXI finishing second tournment mode
Sephiroth FFVII finishing fourth tournment mode
Sphere Mode and Free Sphere Mode finishing all tournment mode
Yangus DQ VIII finishing third tournment mode
Yuna FFX finishing second tournment mode
Zesika (Jessica) DQVIII complete the first tournament
Alfga Road (DQ I-III) clear 1st & 2nd row stages in tournament mode
Nalbina Fortress (FF XII) clear 3rd & 4th row stages in sphere mode
Rabanastre (FF XII) clear 3rd & 4th row stages in tournament mode
Sky City (DQ IV) clear 1st & 2nd row stages in sphere mode
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NES Itadaki Street: Watashi no Oten Niyottete
PS Itadaki Street: Gorgeous King
PS2 Dragon Quest & Final Fantasy in Itadaki Street Special
(don't specify) Itadaki Street3
PSP Dragon Quest & Final Fantasy in Itadaki Street Portable
SNES Itadaki Street 2: Neon Sign wa Bara Iro ni