Marceline and Princess Bubblegum journey to the imposing, beautiful Glass Kingdom, and deep into their tumultuous past, to prevent an earthshaking catastrophe.
This movie contains 12 potentially triggering events.
There's a mutant wolf monster who has their soul sucked out, which isn't technically death in this universe, but it isn't returned, so it's basically the same. The wolf's cub is shown mourning as well, so the impact is the same.
While there is no consistent or intentional child abuse, there is a difficult relationship between a single mother and her young daughter which include the mother yelling once or twice, lying to her (albeit with good intentions), and making some mistakes that end up scarring her for life, and this is a prominent theme in the special. Proceed with caution.
There is a character who is in the form of a dragon for most of the special, but discards the dragon body at the end because it acted as a cocoon. The dragon body is shown lifeless, which could be close enough imagery. Proceed with caution.
There aren't any graphic scenes of amputation, but multiple people made of glass have body parts get broken off, including one who is broken in half. There is also a human amputee character at the end who is missing his right arm, but this happened during the original show and is not discussed here. The original show DOES have multiple scenes of amputation (amputated, grown back with magic, and amputated again for good) with the main character and depicts this character adjusting to it with and without prosthetics.
A glass person gets squashed, and 3 glass peoples' heads also shatter due to a high note (which might be close enough), but none of this is graphic since they are made of glass.
No bones are broken, but there are characters made of glass whose bodies get cracked, broken, or shattered, which may be equivalent. This is not graphic and does not bring them any pain, but proceed with caution.
There is a moment where it seems like a child could be dead, and there is a joke about him not breathing, but he's okay because he's made of glass and doesn't have the same physical boundaries as humans do.
A parent is shown to be deathly ill, coughing up blood, but she sends her child away and dies off screen. The affect of this death on her child is a prominent theme in the special.
we see bonnie and Marcy (who are in a relationship) arguing, and we get flashbacks of them breaking up a long time ago. theres no cheating i just feel like this is worth mentioning
Marcy is heavily coded to be mentally ill after the trauma in her life and she lives in a post apocalyptic world that sometimes requires violence to survive
No one in the episode is depicted as claustrophobic, but a large dragon is trapped in a cave for most of the episode, and there is a scene that takes place within said cave while it's threatening to collapse.
There is a woman of color who dies offscreen in a flashback, but it's not clear what her race or ethnicity is, and she isn't killed off or treated as disposable because of her race; she's just a human in an environment that's not sustainable for human life.
There is a scene where a character coughs up blood, but it isn't excessive or detailed. There are also scenes of blood being tested in a scientific context. There are also a few scenes with characters who are made of glass being broken or shattered in ways that are abstract because they're made of glass, but could still be disturbing to some.
While it is not discussed or depicted in this particular special, the backstory of Adventure Time's heavily centers around worldwide nuclear fallout. Multiple flashbacks in this special take place in the resulting wasteland and have imagery such as bomb shelters and signs of death and decay, and one character is implied to have nuclear radiation poisoning.