Nebulas originally looked like small green creatures hiding inside a black, egg-shaped metal shell 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 eyes, orange arms and white gloves. Their shell had a hole on the bottom where a small cannon was equipped and a yellow propeller on top.
From Sonic Lost World onward, the Nebulas' designs were slightly altered. Their metal shell is now green and the creature hiding inside it is black with cyan eyes. Due their size, the Nebulas' arms are outside their protective shell and are holding control sticks on their hands.
Sonic the Hedgehog 2
First appearing in Sonic the Hedgehog 2, these Badniks are featured in Sky Chase Zone, where the player controls Sonic with his Tornado that is piloted by Tails (and vice versa). In this game, the Nebulas are always hovering in one place, but will start to move up and above the player as they come close, and move down as the player passes them. If the player get below them, the Nebulas start dropping spiked balls on the player.
The Nebulas appear in different formations as the player progresses through the Zone. The first Nebula the player meets is flying alone, but the rest attack in groups of three to seven. The most general formation they use are three in row and near end of the zone.
In Sonic Lost World, Nebulas float around in groups and chains, but they do not fire spike balls from their cannons. During the game, all of Dr. Eggman's Badniks, including the Nebulas, got hijacked by the Deadly Six.
In Tropical Coast Zone 3, Frozen FactoryZone Act 3 and Lava Mountain Zone 2, the Nebulas can be found hovering in one place, most of where the player can use them to reach Grind Rails or cross over volatile minecarts. However, in Trophical Coast Zone ?, Nebulas hover upwards while leaving small air hole for the player to pass through, and in Hidden World Zone 2, they suddenly appear from clouds in groups which the player has to avoid.
In Sonic Runners, Nebulas are one of the most common enemies in the power type characters' stages. Like in Sonic Lost World, they do not fire spike balls from their cannons and instead only appear separately or in groups.
Nebula in Sonic Runners come in three types. Aside from the regular types, there are golden Nebulas that give three hundred extra points each when destroyed, and black ones called Super Nebulas that only Color Powers and power type characters can destroy. Any type of Nebula contains Animals inside them.
Nebula hovers in place waiting for the player to approach. When Tornado comes close to it, the Nebula flies upwards a little and drops small, flashing spiked balls from a shoot on its underside. These Badniks can be found on different formats, that are mostly two or three on rows. Aside from these, Nebula Badniks are relatively harmless, although they frequently appear in groups.
In Sonic Mania, a Nebula model called the Cactula appears in Mirage Saloon Zone Act 1. They are disguised as cactuses in the Zone. When Sonic and/or Tails gets near them, they reveal themselves and start flying around.
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.