A character has somehow been transferred to another plane of existence. Not ascended to a higher one, mind you. This is just an invisible world sitting "on top" of the one we live in. Beings trapped in it can observe our world and move around in it, but are unable to interact with anything or anyone. Their friends will not be able to see or hear them, and they will pass straight through any solid objects they come across. Some variations involve the character leaving their body behind in the physical world, but others have them disappear from this world entirely. Generally speaking, this trope should only include living characters, since we have other tropes for ghosts and spirits. Other residents of the astral plane may include magical creatures, spirits, ghosts, Energy Beings, or even just a whole crew of other humans who were trapped in it over the years. Science fiction variations are also possible, but are less likely to be already inhabited when a character enters one. Subtrope of Layered World. May overlap with Phantom Zone, Spirit World and Astral Projection (often combined with Power Incontinence or An Astral Projection, Not a Ghost). If the trapped character finds someone who can see the astral plane, expect them to ask "You Can See Me??"
- Superman and Supergirl
- Pre Crisis, when they would travel back in time to a time when they were already around they would turn into ghostlike beings, able to see the world but not interact with it.
- Tear-jerkingly referenced in Whatever Happened to the Man of Tomorrow??, after Supergirl died during Crisis on Infinite Earths. A younger Supergirl time travels forward to visit Superman, and is surprised that she's not a ghost. Superman covers by saying that present-day Supergirl is in the future visiting the Legion Of Superheroes.
- In The Skin Jacker Trilogy, children who get lost on their way to the afterlife (or who are in a coma) go to Everlost, which is the same as Earth, except invisible to living humans, and the only "solid" objects in it are places and objects that were greatly loved and/or left its mark on history. Certain children can interact with the living world by "possessing" living humans or "ripping" objects out of the living world into Everlost.
- Sophie's World has a variation on this, in which all fictional characters, including Sophie herself exist in a world on top of the "real" one, able to observe real people, but generally not being able to interact with them.
- Star Trek: The Next Generation Due to a transporter malfunction Geordi & Ro are phased out of sync with the rest of the universe. They can see everyone else but nobody can see them, so people think they're dead.
- Sliders episode "Gillian of the Spirits". This happens to Quinn when the wormhole gets struck by lightning.
- Charmed had more than one example, including an episode where Piper and Leo ended up on another plane thanks to a plot of Gideon's, and an episode where Piper was badly wounded by some demons and ended up on the astral plane, where she met Cole.
- Stargate SG1
- In one episode Daniel ends up on another plane thanks to a crystal skull that was also an alien teleport device. Only his grandfather, who had been exposed to the device before could see him. For a while he thought he'd died, before the truth came out.
- In another episode, Carter and Daniel get stuck in another plane of existence and can only communicate with the rest of the world by tapping the keys on the device that trapped them there in the first place.
- SCP Foundation, #451 "Mister Lonely". He's a former agent, who can be detected by the Foundation but he can't perceive them. At first, he thought that everyone else had vanished.
- Magus from El Goonish Shive is actually from another universe altogether, but a spell gone wrong caused him to end up in the spirit plane of the "main" Gooniverse, which is also inhabited by immortals.
- In Avatar: The Last Airbender, Aang (being the Avatar and all) is more spiritually-attuned than most, and has had to travel to the Spirit World on several occasions. During at least one instance was Aang permanently trapped there with no knowledge of how to escape. Luckily for Aang, he's bailed out by his past life, Avatar Roku.
- In the Aladdin: The Series episode "As The Netherworld Turns", Iago and Abu are sent to the Netherworld by the Eye of Gazeem, an artifact they find in Jafar's old lab. They can't interact with anyone living and no one can see or hear them, and the only way they can communicate is through people's dreams.
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