Unidasu

"The Orbinauts return as one of Sonic's most challenging Badnicks! Pay close attention, you only have a split second to defeat them."

- Profile, Sonic the Hedgehog 4: Episode I website

The Unidasu (ウニダス), also known as Orbinaut and Spike Spinner, is a recurring enemy in the Sonic the Hedgehog series. Making first appearance in Sonic the Hedgehog (1991), Unidasu is a Badnik variant and an Orbinaut model created by Dr. Eggman that sends the four spiked balls around it forward when an enemy is spotted.

Appearance
Being part of Sea Urchin-like Orbinaut series, Unidasu as a Badnik has a similar appearance compared to other Orbinaut variations. In their neutral base form, they have a blue spherical body with wide eyes and four red spiked balls orbiting their body. Once it notices its target, its blue body changes into red. They usually have black eyes, but had cyan eyes in Sonic Lost World.

In Sonic Adventure and Sonic Adventure 2, Unidasu received separate robot models, which belong to E-Series (see Variants section). Compared to regular Unidasu Badniks, these E-series models retain darker color scheme with addition of explosive spiked balls and small motors on their back.

Powers and abilities
Unidasu floats in passageways looking blue and neutral, their spike balls orbiting their body. Unlike Uni Uni though, once the victim comes into Unidasu's sight, the Badnik gets angry and changes its color scheme. It then starts firing its spike balls straight towards its target. Spike balls are usually released in order from beneath its core, moving at a slow speed. However as these Badniks can be placed on underwater sections, avoiding spiked balls is difficult due to heavier movement. They are usually seen orbiting their spiked balls laterally, but in Sonic Lost World though, they are occasionally seen orbiting them horizontally.

Sonic the Hedgehog (1991)
First appearing in the original Sonic the Hedgehog, these Orbinauts travel almost all the time at underwater sections of Labyrinth Zone. These Badniks usually are conformed at cramped passages, thus obstructing the player's way. The player should duck to avoid its released spike balls, and then defeat it with Spin Jump when they become totally defenseless. They later appear in the third act of Scrap Brain Zone.

In the 8-bit the game with same name, these Orbinauts once again appear in Labyrinth Zone. The appearance of these Badniks is also different, as they have a light blue core. It behaves identically to its 16-bit counterpart, but like all Badniks in Master System and Game Gear titles, it doesn't have Animals as a power source.

Sonic the Hedgehog 4: Episode I
Both Uni Uni and Unidasu variants make a reappearance in Sonic the Hedgehog 4: Episode I, as both types appear in Lost Labyrinth Zone with slightly upgraded models. Despite that, both types appear to have similar attack patterns. However, Unidasu (the Badnik is being referred to as Spike Spinners ) now defaults to a red-hot appearance when encountering Sonic.

Sonic Lost World
Both Unidasu and Uni Uni types of Orbinauts make appearance in both versions of Sonic Lost World. During the game, it turns out that Badniks (Orbinauts included) got hijacked by the Deadly Six. In the Wii U version of the game, Unidasu types can be found at Frozen Factory Zone 4 and Sky Road Zones 1 and 4. Normally, Unidasu is seen hovering around with spinning spike balls, while having a neutral form. In side-scrolling, 2.5D sections, they are seen orbiting their spike balls laterally, while both Unidasu and Uni Uni types come together in stacks to create huge enemy wall. In 3D sections of the game, they are orbiting horizontally instead. Unlike Uni Uni types, when the player comes close on the Unidasu, it will turn into red and throw all spike balls to the lateral direction, while making itself completely defenseless.

In the Nintendo 3DS version of the game, Unidasus are featured at the Casino-themed Sky Road Zone 2, where they are seen only in 3D sections instead. Unlike the Wii U version, Unidasu types will never fire their spike balls or turn red and rather move around with their spike balls. The player has to avoid hitting on spike balls while targeting on the core body. By using Indigo Asteroid Color Power, Unidasu can be easily defeated, although they start respond after destroying one of them.

E-15 Spiky Spinner
E-15 Spiky Spinners (also renamed Spiky Spinner and later re-translated Unidus) appear in Sonic Adventure and later in Sonic Rivals 2 as collectible card. Spiky Spinners are part of the E-Series and they patrol Speed Highway and the Sky Deck with two attack patterns.

E-32 Unidus
An upgraded model E-32 Unidus appears in Sonic Adventure 2, dubbed also simply as Unidus. As part of the E-Series, they can be found at Hidden Base and Death Chamber. Unlike its previous model, Unidus do not throw its spikes away but keeps bustling around.

Archie Comics
In the Sonic the Hedgehog comic series and its spin-offs published by Archie Comics, a small team of Orbinauts suddenly attack to Sonic and the group in deep underwater of Labyrinth Zone. As Sonic discovers a hole in underwater wall and breaks it, he manages to create the column and thus the underwater vortex, which sucked in Sonic, Sally, Rotor, Antoine and Orbinauts in. As all of them now are sliding down the waterfall, Sonic and Sally manages to jump to the other side as receiving the hand grip of Rotor. Unfortunately, Antoine and Orbinauts fall down to the pit, however being seen to survive at Scrap Brain Zone in later.

The appearance is similar to a specific one from Robotnik's badnik army in early issues, having a dark blue orb and grey spike balls. Instead of the balls themselves, these Orbinauts actually shoot spikes from spike balls. Oddly enough, the Orbinauts also have mouths.

Trivia

 * In Sonic X #11, the Uni Unis at a virtual reality version of Star Light Zone are seen having the Unidasu's color scheme.
 * Orbinaut is one of the Badniks that hasn't been featured in character bios of Sonic Archives.