Nebula Ghosts are the main antagonists of Space Mountain: Ghost Galaxy, the Halloween overlay for Space Mountain in Disneyland in California and Hong Kong Disneyland. They are a group of massive, skeleton-shaped sentient nebulae that seek to destroy and kill humans and everything they have sent up into space.
Everything seems normal on Space Mountain until one day, when strange cosmic storms begin barraging the space station and vehicles, including a large green one over the planet that cuts off audio and visual signal transmission. As guests travel through the domed area, strange, colorful storm nebulae form outside, which surround and leave claw-like scratch marks on the dome. Guests enter their vehicles and are about to be launched into the space part of the Mountain, but are interrupted when a massive red nebula resembling a skeleton suddenly comes to life and attacks, electrifying the runway. As the vehicles continue to move, more nebulae come to life, and one grabs at the vehicles as they speed away. With the vehicles now speeding through the area, the nebula ghosts attack them at every turn by grabbing or biting at them, including lunging at them with their arms or trying to scratch them. However, the guests make it into a tunnel to lead them back to the docking area. One more ghost arrives for one last scare before guests arrive safely back.
The Nebula Ghosts seem feral and violent, and do not speak other than high-pitched shrieks and growls. However, they clearly despise humans (and possibly all living things), and seek to kill them and destroy any man-made object sent into space. While it is unknown why they act this way, it can be assumed that they either see this as pollution or as interference in their territory, or they are simply misanthropic monsters that want to kill humans.