The classic Nebulas look like small green creatures hiding inside black, egg-shaped metal shells that they control by seemingly clutching a pair of control levers. It is unclear what these creatures fully look like, but they do have two cartoony black eyes, orange arms and faces, and white gloves. Each of their shells also have a hole on the bottom where a small cannon is equipped, and a yellow propeller on top.
In Sonic Lost World and several subsequent games, the Nebulas' design was slightly altered. Their metal shells became green and the creature hiding inside became black with cyan eyes. Due their size, the Nebulas' arms were also moved outside their protective shells, where they held control sticks in their hands.
In Sonic Forces, the Nebulas received a more modernized and militaristic design. These Nebulas were designed to resemble white-gray eggs with red-eyed black faces on their upper fronts, a wide propeller on their tops, and a small cannon on their bottoms.
Sonic the Hedgehog 2 (16-bit)
The first appearance of this Badnik was in the 16-bit version of Sonic the Hedgehog 2, where it served as an enemy. This time around, this Badnik is referred to as Nebula (ポトス,Potosu?). In this game, the player encounters them in Sky Chase Zone, where the player controls Sonic with his Tornado that is piloted by Tails (and vice versa).
In gameplay, the Nebulas start out by hovering in one place, but will start to move up and above the player a little when they come close. They will similarly move down after the player passes them. If the player get below them, the Nebulas will start dropping small, flashing spiked balls, which inflict damage, on the player.
The Nebulas appear in different formations as the player progresses through Sky Chase Zone. The first Nebula the player meets is flying alone, but the rest will attack in groups of three to seven. The most general formation they use are three in row. Also, destroying a Nebula will release an Animal from inside it.
In gameplay, the Nebulas behave and attack exactly like how they did in Sonic the Hedgehog 2. They appear mostly in the same formations, even through these Badniks only appear in two or three rows. Also, when destroying a Nebula, an Animal will be released from inside it.
Sonic Rivals 2
In Sonic Rivals 2, the Nebula made an appearance on the 71st collectible card in the game. To collect it, the player has to either get the high score in Blue Coast Zone Act 1 or unlock the Chao Detector in Blue Coast Zone.
Sonic Lost World
In the Wii U/PC version of Sonic Lost World, the Nebulas returned as enemies. In this game, they received a cartoony redesign. During the game, all of Dr. Eggman's Badniks, including the Nebulas, got hijacked by the Deadly Six after the group betrayed the Doctor.
In gameplay, the Nebulas float around in groups or chains, but they do not fire spike balls from their cannons. In Tropical CoastZone 3, Frozen Factory Zone 3 and Lava Mountain Zone 2, the Nebulas can be found hovering in one place, mostly for the purpose of allowing the player to use them to reach Grind Rails or cross over volatile minecarts. However, in Tropical Coast Zone ?, Nebulas hover upwards with some distance between them so that the player can pass in-between them. Also, in Hidden World Zone 2, they suddenly appear from clouds in groups which the player has to avoid. In addition, when destroying a Nebula, an Animal will be released from inside it.
In gameplay, when Nebulas appear, they attack by dropping spike balls in intervals before eventually slamming themselves downwards. Both of these attacks will cause the player to fall below the screen to an instant death if they touch the playable character.
Sonic Runners series
In Sonic Runners, the Nebulas appear as enemies. In this game, they retain their design from Sonic Lost World. They are also one the most common foes in the power type characters' stages. In gameplay, they do not fire spike balls from their cannons. Instead, they appear either separately or in groups. Some are stationary.
Nebulas in Sonic Runners come in three types. Aside from the regular Nebulas, there are golden Nebulas that give 300 extra points each when destroyed, and black ones called Super Nebulas that only Color Powers and power type characters can destroy. Also, any type of Nebula contain Animals inside them.
In gameplay, the Nebulas both appear on their own and in groups. They also hover in stationary positions. In some stages, they do nothing, and in others, they drop bombs. Overall, they are weak enemies that are taken out with just one attack. They are also often arranged in midair so they form chains that the player can skip cross using the Homing Attack/Wire Attack.
The Cactula is a camouflage-orientated variant of the Nebula. These variants have all of the regular Nebula's abilities, but can also disguise themselves as cactuses in their native Zone. They first appeared in Sonic Mania.
In the Sonic the Comic series published by Fleetway, the Nebulas were standard flying units in Dr. Robotnik's Badnik army. During the comic's run, Nebula Badniks demonstrated the ability to aim their projectiles at their target rather than simply dropping them. Robotnik used the Nebulas for countless attacks on various Zone until his downfall from an electromagnetic pulse which disabled all his Nebulas, although they would be revived over time.