Of all the enemies in the game, Demi-Human enemies have the same palette between enemies and allied monsters. However, unused alternate palettes do exist for every Demi-Human. For Demi-humans from previous Mana games, the alternate palettes used happen to be alternate palettes from the previous games, as well.
Contributed by TomGuycott
At Christie's Palace in Geo, the section called the Bronze Auditorium contains a number of different statues. Fans of the series might recognize six of the statues as the six main playable characters of Seiken Densetsu 3, the predecessor of Legend of Mana that was only released in Japan on the Super Famicom.

In addition, the Storage Room below contains statues of Gildervine, Bigieu and Death Jester from Seiken Densetsu 3, as well as the Mana Beast from Secret of Mana.
Contributed by TomGuycott