The Super XX appears in various forms throughout most of the Sonic Wings series. It first appears as Super X Kai, a green hovering craft shaped somewhat like a flying saucer. This later proves to the be the "head" of the vehicle; its "body" is a four-legged vehicle reminiscent of the AT-AT walkers in the Star Wars saga. In Sonic Wings Special, Super X Kai also attaches itself to a building to become the head of the Tokion robot. Super XX possibly takes its name from an aircraft named the Super X in the Godzilla series.
Super X Kai, the head of what will in later games be Super XX, first appears as a large, green, hovering aircraft which bursts out of a building at the end of the Japan stage. It shoots fireballs and extends long, mechanical arms to attack. The craft is marked with the kanji 改 ("kai"), meaning "revision."
The full Super XX first appears in Sonic Wings 2. The Super X Kai bursts out of a building early in the stage and disappears deeper into Tokyo. At the end of the stage, it comes out of a shinkansen (bullet train) station, as it did from a building in Sonic Wings. The Kai attaches itself to the head of the walker, and the whole contraption then walks backward over the train tracks (and trains) while shooting at the player's aircraft.
Stage: Tokyo (Super X Kai, Tokion), Grand Canyon (Super XX)
Both sections of Super XX appear in Sonic Wings Special, with Kai showing up at the end of the first stage in the game. It again bursts out of a building and shoots at the player. Much later in the game, the Super XX walker appears as the boss of the Grand Canyon stage, without showing the Kai as a separate craft. Super XX again walks backwards and shoots at the aircraft, leaving tracks in the sand.
After defeating the game with any character, the Tokyo level changes in some areas if replayed with that character. Now during the boss fight, instead of bursting from the building, the Super X Kai attaches itself to the top, and the whole building comes to life as a giant robot, Tokion.
Stage: Mato Grosso (Super XX)
Super X Kai does not appear in Limited, but the walker is the boss of the Mato Grosso stage. It behaves the same as it does in Special.
Status: minor boss
Found in Tokyo, the Super X Walker puts the imperial Walkers to shame. As tall as this monster appears, you won't have too much trouble knocking it to the ground. Before it takes out too many buildings, feed it full of lead.
-Aerofighters Assault English game manual
The Super XX walker is the first boss encountered in Assault and therefore fairly easy to take down. It is best defeated by firing at it while flying at a low altitude.
Stage: Tokyo (Super X Kai), Grand Canyon (Super XX)
Super X Kai serves as the boss of the first level of the game, bursting out of the buildings in Tokyo and shooting at the player. As in the original Sonic Wings Special, the Super XX walker is later the boss of the Grand Canyon.