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 past."
- In Young Justice, Secret spent most of the series trapped between the world of the living and that of the dead as a result of her evil brother sacrificing her as part of a ritual to gain powers. The final issue has her turned back into a normal girl.
- In Project Superpowers, Fighting Yank dies and becomes stuck on the astral plane after he agrees to take his ancestor's place in exchange for receiving enough power to save his friends from a deadly situation.
- The Authority: One arc had a supervillain's organization kidnap baby Jenny, them and their base overlapping with New York while being invisible and intangible explained away as existing at different vibrational frequencies.
- In Astro City, the Body Surfer supervillain called the Silver Brain was banished to another plane of existence years ago by the Samaritan. He keeps escaping by possessing the denizens of that other realm and riding their bodies back to the physical world.
- In Death Defying Doctor Mirage, the original Doctor Mirage, Hwen, has been trapped in the Deadlands for over four years after misplacing an artifact that belonged to one of the Deadlands' more powerful locals. The first arc involves his wife Shan making a journey to find him and bring him home.
- As long as there are believers, the Guardians in DreamWorks' Rise of the Guardians are large and strong and able to influence events on Earth. However, to nonbelievers, the Guardians are invisible and immaterial, almost to the point of being nonexistent. Also, as their believer count dwindles, so does the Guardians' size and strength.
- Coco: Miguel, in a attempt to borrow a guitar from his idol during the Dia de Muertos, becomes invisible to the human world, but starts to see the dead, in skeleton forms, including members of his family.
- What happens to Dalton in Insidious, where his soul is trapped in The Further and the other characters have to help him get back into his body before some other malevolent spirits try to take possession of it for themselves.
- 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.
- This is indicated to be Sauron's ultimate fate at the end of The Lord of the Rings. Technically he cannot really die until Arda itself is unmade by the creator God, but his second defeat and the destruction of the One Ring has reduced him to a powerless spirit unable to build another body for himself, still wandering the world but unable to influence it in any way. Meanwhile, his former boss Morgoth is trapped in the Void Between the Worlds outside Arda.
- The Zack Files book "I'm Out of My Body...Please Leave A Message" features the title character Zack and his best friend Spencer screwing around with a book that allowed them to astral project. While they eventually get the hang of it and leave their bodies, they end up unable to figure out how to return and the book is mostly about them attempting to reenter their bodies.
- At the start of the seventh Warrior Cats arc, after Bramblestar loses a life, he is unable to return to his body since some unknown being has begun to possess it, leaving his spirit stuck and running desperately around the territories, visible only to Rootpaw.
- Agents of S.H.I.E.L.D.: In "Deals with Our Devils", after Coulson, Fitz and Robbie got caught in an explosion created from a Darkhold experiment, they are stuck and falling into Hell Dimension. They see the real world in a sephia tone, which gradually gets darker, and can't interact with it except for subtle influences in electronics. To make things worse, the Ghost Rider isn't too keen on being dragged down with Robbie and possesses Mack.
- Star Trek: The Next Generation:
- In "The Next Phase", 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. Eventually, they manage to find a way to contact the rest of their crew members, who then manage to phase them back.
- In "Realm of Fear" Lt. Barclay thinks he's seeing things while being tranpsorted and thinks he has Transporter Psychosis, but he's actually seeing some people trapped in whatever they transport through when using the transporter. Barclay grabs one of them and hauls him back into reality, and then some security officers are sent in to rescue the rest.
- Star Trek: Enterprise: In "Vanishing Point", Hoshi Sato is terrified of using the first generation of transporters. When she does use it, her worst fears are realized when she slowly starts to vanish from existence. Eventually, she fades away, still being able to travel the ship but nobody around her being able to hear or see her. Eventually, she realizes that a group of aliens are somehow involved, which all turns out to be subversion when she emerges from the transporter, the entire thing having been a nightmare she experienced in the split second before she rematerialized.
- Sliders episode "Gillian of the Spirits". This happens to Quinn when the wormhole gets struck by lightning. Particularly unfortunate as the slider got fried during the transition and his friends have trouble repairing it without him.
- Charmed (1998) 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 Mitchell 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. They tried communicating with Daniel since he'd been in that situation before, only to be ignored by him, showing that it was a different plane from the crystal skull incident.
- Space Cases:
- In the episode "Nowhere Man", Harlan is accidentally blasted into another dimension, becoming incapable of interacting with the physical world or being seen by his teammates. The only thing he can interact with is an instrument that was blasted with him... and it's showing imminent danger. His plight isn't discovered until Radu's superhuman hearing picks up his pleas for help. The other kids ultimate find a way to restore him.
- At the end of the first season, Catalina is shunted off into another reality in an explosion. As a side-effect, her friend Suzie, previously believed to be imaginary, ends up physically manifesting aboard the Christa.
- From the book 'The Devil' in The Arcana, the protagonist has their body used as a ritual to summon Count Lucio from the dead and finds themselves trapped between the worlds of living and dead, able to see the other characters but not touch them, and capable of only the faintest possible interaction.
- 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.
- Adventure Time: In "Beyond This Earthly Realm", Finn gets trapped in the astral plane after touching an ancient artifact, where all of the spirits roam. Much to his chagrin, the only one who can see him is the one person who can see into the supernatural realm, the Ice King.
- 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.
- In the first season finale of DuckTales (2017), Lena appears to have been obliterated by a magic spell, but the audience sees (and Webby suspects) that she was Only Mostly Dead. Midway into the next season, Webby has found out she was sent to the Shadow Realm, and the audience see her watching over Webby from there. By the end of the episode, Lena manages to get out.
- Gravity Falls: In "Sock Opera", Dipper is possessed by Bill Cipher, temporarily trapping his spirit as a ghost that can only interact with the rest of the world through possessing an inanimate object. According to a note Bill left in Gravity Falls: Journal 3, if Dipper's body died while his spirit was wandering (which Bill planned to cause), he'd have been stuck there forever.
- 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, Aang was in danger of being permanently trapped there with no knowledge of how to escape. Luckily for Aang, he's bailed out by his past Avatar incarnation, Avatar Roku.
- In the debut episode of the Sheep Talisman on Jackie Chan Adventures, Jade messes around with the Talisman and ends up stuck in the Astral plane after Shendu astral projects his spirit into her unoccupied body. Fortunately, she's able to enter Jackie's dreams and alert him to what happened.
- In the Transformers Aligned Universe opening two groundbridges/spacebridges within close proximity to each other will cause them to warp the space between them, sending anything between them into the 'Shadowzone'
- Characters in Transformers: Prime speculate that anything in the Shadowzone is moving at a higher frequency than the normal world, meaning that they phase through matter and any sound becomes so high-pitched that it's imperceptible, though electromagnetic signals are not noticeably affected. The only way out of the Shadowzone is to be between two groundbridges once more while inside the Shadowzone.
- This ends up being the way the heroes defeat Soundwave - since he is directly connected to the villains' spacebridge's systems, he can summon a portal anywhere he wants, that goes anywhere he wants, with great speed and accuracy, and it's often that the heroes attack Soundwave and find themselves stepping right into a spacebridge that beams them right off the battlefield or into a trap. So they feint an attack to get him to open his to defend his front, whereupon they open their own behind him, sending him straight to the Shadowzone.
- Not that this stops Soundwave forever - years later, he's finally near a groundbridge when it is opened, and surprises everyone present by opening his own completely unannounced. While he is re-trapped at the end of the episode, he has proven that any activation of a groundbridge runs the risk of him escaping again.