The Hover Unit appears mostly in the SatAM series, where it serves as the primary means of transport for Dr. Robotnik's military forces, piloted by his SWATbot army. There were several variations, though they all maintained the same overall design and appearance. On rare occasions, the Knothole Freedom Fighters were able to commandeer these craft and employ them against Robotnik, either to counteract one of his latest plans or as a covert means of infiltrating his operations.
The Hover Units were far less frequently seen in the Archie Comics, but did make occasional appearances. In the "EndGame" storyline, a Hover Unit attacked the transport carrying Sonic the Hedgehog and others to the Devil's Gulag prison, allowing Sonic the opportunity to escape custody and clear his name after he'd been framed for the attempted assassination of Princess Sally Acorn. In issue #29 of Knuckles the Echidna, Sally pilots a Hover Unit when she travels to Angel Island in an attempt to enlist the support of the Brotherhood of Guardians in the Kingdom of Acorns' war against the Eggman Empire.
Design and Abilities
The Hover Unit's primary design is of an egg-shaped hovercraft with two hatches on both sides near the rear of the craft to allow entry and exit (some models also featuring an alternate roof hatch and loading ramp on the underside). There are two seats for a pilot and co-pilot at the front of the craft, and the cabin can be modified to suit the needs of the mission being performed at the time. The Hover Unit generally features a two-tone dark grey/black paint scheme, though in the SatAM episode Sonic Racer several Hover Units were seen in varying colors participating in a race Robotnik was holding as a trap to catch Sonic. Robotnik also had a personal hovercraft which featured a red and black paint scheme. The Hover Unit is also used as an attack craft; its typical armament consisting of one or more laser cannons mounted on the exterior of the craft. Robotnik's personal hovercraft was further armed with a missile launcher and cloaking device, which allowed him to escape undetected when several of his plans backfired on him. The Hover Units were also equipped with various sensors for use in patrolling Robotropolis, such as searchlights and Infra-Red sensors for detecting heat signatures of organic intruders (though these could be confused by emissions from power stations within the city, as seen in the episode Sonic and Sally). The Hover Units are also shown being capable of flying in space and surviving planetary re-entry, as seen when Sonic and Rotor Walrus commandeer one to escape an exploding space station in the episode Harmonic Sonic.
A similar-designed vehicle, but yellow/peach in coloration instead. The "Auto Unit" is apparently a non-flying variant of the Hover Unit that is used in performing repairs and maintenance all throughout Robotropolis, to get around from location to location quickly. The "Auto Unit" employs a series of hovering platforms that allow it to reach it's destination almost as fast as the Hover Units. In vehicular mode, the "Auto Unit" relies on four wheels for mobility, but it can shift into a more bipedal mode, with the axles forming as arms and legs to move about, and the tires serving as the Units ankle and wrist joints. Though it's cockpit is designed similarly to it's flight-bound brethren, the "Auto Unit" is uniquely smaller on the inside, only large enough to accommodate a single Mobian/Robian driver alone (Probably because of all the mechanical equipment aboard to allow the "Auto Unit" to shift from vehicle to bipedal mode easily), or runs from an onboard AI (presumed). The "Auto Unit" also possesses a laser cannon like the Hover Unit, but is located on the underside as opposed to the roof like the Hover Units. These only appeared in two episodes of SatAM, one was used by Sally to sneak into Robotropolis to assist Sonic, Antoine Depardieu, and Cat in gathering intel on Robotnik. Later on, two more were chasing Sonic through a factory, only to get the drop on them when Sonic knocked over a pile of parts atop them.
"Auto Unit" is not the official name of the vehicle as it is unnamed in the series.