The Nebula is a rotund Badnik that looks to be a small, green creature hiding inside a metallic black shell. It has a frowning pair of eyes and two stubby arms which are perpetually grasping two joysticks. The top hemisphere of the shell is topped with a helicopter rotor that allows the Nebula to fly. The bottom hemisphere is equipped with a bomb tube from which the Nebula drops small spiked bombs.
Sonic the Hedgehog 2
In their debut appearance, Nebulas are encountered in the Sky Chase Zone as part of the Badnik aerial force defending Dr. Eggman's Wing Fortress. They appear in different formations throughout the length of the stage, and as the Tornado approaches they will rise higher into the air in order to drop their bombs on the player. They are slow to ascend, though it may be easier for the player to dispatch them without taking damage by attacking while nearer the right side of the screen.
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 and chains, but they do not release bombs from their cannons. In Tropical Coast Zone 3, Frozen Factory Zone 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 Sonic Forces, Nebulas have been given a more militarized design along with all other Badniks in the game. Their spherical bodies are completely green save for a small black featureless face with red optics. This new model also has no arms.
Nebulas appear in numerous stages throughout the game, usually in chains for Sonic to move along using his Homing Attack, or otherwise in large groups. These Nebulas always appear stationary, hovering in one place while periodically dropping bombs.
Sonic the Comic
Nebulas have made numerous appearances throughout the Fleetway Editions' Sonic the Comic series. Depending on the artist, their appearance would sometimes change. Nebulas were a mainstay of Dr. Robotnik's aerial forces during his rule over Mobius before his empire was crippled by a worldwide electromagnetic pulse. Even after the fall of his empire, Robotnik would continue building these robots along with new Badnik models. In the comic, Nebulas were seen to be able to aim their projectiles rather than just dropping them on whatever was directly underneath them.