Two men are disposing of a vaguely-defined, toxic liquid at a dump, when a monster rises out of the liquid. Meanwhile, Winston is cleaning the car while Slimer is eating a lollipop and pretending to drive it. Winston tells Slimer not to eat in the car, so he hides the lollipop behind his back, but it gets stuck. Then, when he unsticks it, he ends up knocking over the soapy water and crashing onto the car door.
They then get called to the dump, where the worker describes the monster. The Ghostbusters and Slimer start searching around, complaining about the pollution. The guys have Slimer scan for the monster, but the P.K.E. meter malfunctions and then the monster shows up. The Ghostbusters try to zap it, but it flies into the car and disappears, and the P.K.E. meter still isn't working.
They get into the car, but it malfunctions, yet they still manage to get home. However, Slimer later sees an image of the monster in the car door instead of his reflection. He tells Winston, but when they get to the car, the image is gone. However, Winston does notice that the Ecto-1 is parked in the wrong place. He thinks one of the guys did it to be funny, but then it turns out, the monster is under the hood. However, it hides when everyone goes to look, and the car is now facing the correct way.
They get another call, and drive off, but then the car stops for no reason. Then, it comes to life and drives off uncontrollably the wrong way, then launches everybody out. Peter, Ray, and Egon try to fire at it, but Winston doesn't want them to damage the car, and then starts trying to reason with it. However, it doesn't work and the car drives off with Winston attached to the front.
The rest give chase and find the car, but no Winston, so they think the possessed Ecto-1 killed him. However, as it turns out, Winston is hiding in a manhole (in his underwear, because it tore off his jumpsuit and boots). The guys and Slimer are sad that they may have to destroy the Ecto-1 for the safety of New York, but when they (except Winston and Slimer) try to do so, it deflects the beams with a forcefield.
They go home, Winston puts a robe on, and they tell Janine the situation. Ray then finds out that some Native Americans believed in a protective Earth spirit, which they surmise might have been the monster and that the ugliness and evil are because of the toxic waste. They borrow Janine's car (despite her being reluctant that they crashed her car last time they borrowed it) and head off.
When they get to the street, they find giant tyre tracks, implying Ecto has grown. Winston tries to think of a plan to lure Ecto somewhere, when the giant Ecto shows up. They drive back to the dump, and Winston climbs into the crane and produces a magnet from it. The rest of them use Janine's car to lure Ecto-1 near the magnet, which weakens the monster. They zap it, which turns it back into an Earth spirit, meaning that they don't need to trap it. Winston then does a speech, blaming humans for pollution and therefore the whole conflict. Then, Ecto-1 wins first prize in a car show.
This episode provides examples of
- All Myths Are True: The episode establishes that an old Native American legend of an Earth spirit is actually true.
- Applied Phlebotinum: We don't know what the liquid that set off the plot is, only that it's toxic, smells bad, can turn benevolent spirits into demons, and is apparently a waste product.
- Artistic License – Chemistry: One guy uses the term "chemicals" to mean "toxic substances". In reality, a chemical just means any element or compound.
- Barbie Doll Anatomy: When Winston is in his undies, he's drawn with no nipples.
- Beauty Equals Goodness: Ray determines that when the monster was a protective spirit, it was less ugly than it is now, but that "that toxic waste turned him ugly in more ways than one".
- Companion Cube: Winston acts as though Ecto-1 is his daughter or girlfriend, even going so far as to try to reason with it. Slimer gets in on the act when he says, "Poor Ecto!" at the thought of it being destroyed. Downplayed for Egon, who also calls her "she", but that's pretty normal for vehicles.
- Continuity Nod: Ray calls Slimer "spud" like he did in the movie.
- Distressed Dude: Winston gets dragged off by the possessed car.
- Dramatic Irony: The audience finds out the monster is in the car before the characters do.
- Ectoplasm: Slimer gets slime on Ecto-1's door.
- Green Aesop: The moral of the episode is not to pollute.
- Green Is Gross: The toxic substance is green.
- Heel–Face Revolving Door: The monster used to be a benevolent spirit before being exposed to toxic waste, which turned it evil, but then being zapped by the Ghostbusters changed it back.
- Humans Are the Real Monsters: The environmentally-destructive behaviour of humans is the true cause of the spirit's corruption. Winston realises this just in time to prevent the spirit being trapped.
- "I Can't Look!" Gesture:
- The dump worker covers his eyes when the monster rises.
- Winston and Slimer cover their eyes and turn away when the other guys fire at Ecto.
- I Don't Think That's Such a Good Idea: Ray doesn't think it's a good idea when Winston tries reasoning with the Ecto-1.
- Literalist Snarking: When Winston tells the other guys to "check [their] boots", they look and say that they're on their feet.
- Narrative Shapeshifting: Slimer morphs into a monster when telling Winston about seeing the monster's image.
- Not So Above It All: Egon joins in on jokingly saying that his boots are on his feet when Winston tells the others to "check [their] boots".
- Quaking with Fear: Slimer shakes nervously when scanning for the monster.
- Red Eyes, Take Warning: The toxic waste monster has red eyes.
- Reports of My Death Were Greatly Exaggerated: Because Winston's clothes were everywhere and he was nowhere to be seen, the rest of the Ghostbusters, plus Slimer, think he was killed, but he actually hid in the drain.
- Running Gag: Winston keeps not wanting the car to get dirty.
- Say My Name:
- Winston yells, "Slimer!" when the latter makes a mess.
- Peter yells, "Winston!" when the car drives off with him attached.
- Slapstick: When removing the lollipop, Slimer bounces off walls and knocks over a bucket of water, drenching Winston.
- Space Whale Aesop: Due to being a supernatural-themed show, the moral can be summed up as "don't pollute, or you'll turn a benevolent deity into a monster and it will rise up and possess someone's car".
- That Makes Me Feel Angry: Janine says, "I'm shocked!" when the guys tell her about Ecto-1 being possessed.
