The film centers around Mara Carlyle and Dylan Hovemeyer who begin dating amidst an epidemic in which kids in their high school senior class begin exploding. As more and more students die and scientists struggle to find a cure, the survivors try to navigate how to live life to its fullest when tomorrow is no longer promised.
Spontaneous contains examples of:
- Bittersweet Ending: Over thirty students (including Dylan) are gone but Mara, Tess and the surviving students are seemingly safe from exploding with the pills being perfected. Mara learns to come to terms with loss and unpredictability, committing to living in the moment and even fulfilling some of her childhood dream (like hanging out in a beach house with Tess).
- Despair Event Horizon: Mara hits this hard after Dylan dies, drinking excessively, engaging in reckless behavior and fighting with Tess.
- Double-Meaning Title: Both about the student deaths and the theme/lesson learned about living life in the moment since tragedy could strike at any moment.
- Empty Piles of Clothing: Well, bloodied piles are all that's left after the explosions. Most notable with Cole, who was wearing motorcross gear when he pops, making it all fall over in flate human shape.
- Giver of Lame Names: Mara complains that the non-scientific name given by the government for the pill which (maybe) is keeping her and her friends from exploding is "the Snooze Button".
- Gory Discretion Shot: None of the first five explosions are directly shown, along with some others later on.
- Heterosexual Life-Partners: Mara and Tess have been best friends since they were very young and have plans to grow old into cool old ladies together.
- Hazmat Suit: How the CDC agents are dressed when they come take Mara and Dylan away after the twins explode while driving to their stash.
- Hope Spot: When when it seems that scientists have created the right medication to keep students from exploding, the students return to school after weeks without an incident. Then kids start exploding at a more rapid rate then before with Dylan being one of them.
- Ludicrous Gibs: Mostly averted. People explode into what's either pure blood or a bloody puree with no identiable tissues. The exception: Part of Dylan's jawbone did manage to hit Mara's forehead.
- Mushroom Samba: After Katelyn's funeral, Mara buys some mushrooms from the dealer twins. She spends her trip with Dylan taking care of her as she hallucinates various copies.
- Not Enough to Bury: Zig-Zagged - We see at least two caskets getting buried, but it's unclear if they're just for show or if whatever blood could be scraped is placed therein.
- Pink Mist: All the remains of most victims.
- "Pop!" Goes the Human: Zig-Zagged - the explosions just happen out of nowhere, with no visible inflation.
- Plot-Triggering Death: In the middle of a pre-calculus class, Katelyn Ogden explodes.
- Riddle for the Ages: The cause of the epidemic is never explained.
- Shout-Out: Dylan is a film buff, so both him and people close to him namedrop Cronenberg, Back to the Future, Traffic (2000), ET, and others. Mara's Halloween costume is from Carrie (1976), though only Dylan recognizes her without the bloody splatter.
- Spontaneous Human Combustion: A variation that sets the plot in motion. While the kids do explode there is no flame just a lot of blood and guts.
- Straight Gay: Implied with Perry Love, whom neither Mara nor Tess knew was gay.
- Their First Time: Sometime after getting released from the tent, Mara takes Dylan's virginity in her room.
- Too Good for This Sinful Earth: Dylan was a sweet hearted good natured fun loving guy who every one in the movie loved and his death changes the film from a pure dark comedic tone to a more dramatic and tragic one.
- Visual Pun: In-Universe, After receiving an anonymous declaration of a crush, Mara insists she doesn't want any dick pic. Her secret admirer, Dylan, sends a picture of Richard Nixon, along with an apology that "it's crooked". He later sent her other pictures various Richards.
