An unused FMV can be found within the data of the game's second disc. The FMV features a song entitled "Stars of Tears", a vocal track performed by Joanne Hogg and composed by Yasunori Mitsuda that doesn't play anywhere else during the game.
The Gazel Ministry's personality data is stored in a supercomputer named SOL-9000, a reference to HAL-9000 from Arthur C. Clarke's novel 2001: A Space Odyssey.
Food in Solaris is processed in a facility called Soylent System, where Spoiler:they transform Wels (mutant human beings) into food. This is a reference to the movie Soylent Green, in which Spoiler:humans are processed into food.
There is a poster of Tifa from Final Fantasy VII inside a house in Class 2 Citizen Sector in Solaris.
Lucca from the game Chrono Trigger makes a cameo appearance in the village of Lahan.
In the last battle against Solaris' special force The Elements (Dominia, Kelvena, Tolone and Seraphita), they merge their animal-shaped Gears into one big super-Gear in a scene which clearly parodies the Mighty Morphing Power Rangers.