The Ghostbusters are on a job, but Egon is concerned because they also need to pick his uncle Cyrus up from the airport. They end up late, so Cyrus catches a taxi instead, and thinks the firehouse looks dingy and like a garage. He talks to Janine and Slimer for a bit, but loses his glasses and mistakes the latter for a cat.
The Ghostbusters arrive and meet Cyrus, who expresses disdain at someone as smart as Egon being an "exterminator" and expresses disbelief in ghosts. The Ghostbusters get another job, and take Cyrus with them to prove that ghosts are real, but he loses his glasses again and doesn't see them.
Cyrus later convinces Egon to be his lab assistant, guilting him by reminding him of a promise he made in his youth to always help his uncle when needed. Egon leaves (albeit reluctantly), leaving a note, that makes Janine cry. Then, the Ghostbusters get a call to Central Park, but they have trouble with just three of them. Meanwhile, Egon is working with the lab rats, but he's bored and misses his old job.
The other Ghostbusters and Janine visit him and decide to see if they can convince Cyrus to let Egon help them, hoping this would change Cyrus's mind. He does let Egon help, and they end up catching the poltergeists, but Cyrus stays behind at the firehouse. There, he messes with the containment unit and sets the Stay Puft Marshmallow Man free.
Janine sends the Ghostbusters an alarm and they drive back to see Stay Puft. Janine, Slimer, and Cyrus (who's now convinced that ghosts are indeed real) jump into the car. Stay Puft is too big to catch in one trap, so the Ghostbusters catch him using four, with Cyrus helping. Cyrus then decides to let Egon keep his own job.
This episode provides examples of
- Alliterative Name: Cyrus's last name is Spengler.
- Animal Testing: The lab Cyrus works at has some rats that they apparently run in mazes.
- Blind Mistake: Cyrus loses his glasses and mistakes Slimer for a cat.
- Blind Without 'Em: Cyrus can barely see at all without his glasses.
- Did You Just Flip Off Cthulhu?:
- During the job at the laundromat, Peter smack-talks one of the ghosts he's trapping.
- Peter later calls the Stay-Puft Marshmallow Man fat to get his attention.
- Ditzy Genius: Cyrus is smart enough to be a scientist, but dumb enough to start fooling around with a machine he knows nothing about.
- Don't Call Me "Sir": Peter wants Cyrus to call him "Peter", not "Dr. Venkman".
- Drives Like Crazy: One guy swerves onto the sidewalk to avoid the ghosts.
- Ectoplasm: Slimer spits goo into Janine's hair.
- Extra Eyes: Some of the background ghosts have more than two eyes, including one with eyes all over its body.
- Filthy Fun: Discussed when Cyrus thinks Slimer is a cat due to bad eyesight and thinks that he feels gooey because he's been playing in mud.
- Grumpy Old Man:
- Cyrus appears to be in his sixties and is a cranky snob.
- At the haunted mall, there are some grumpy old women, who angrily fight over clothes.
- I Ate WHAT?!: When Janine sees Slimer sitting in the water cooler, she hopes he hasn't done that before.
- I Gave My Word: Egon feels bound by a promise he made to his uncle years ago to leave and work for him after Cyrus asks for his help.
- Instantly Proven Wrong: Ray says that he and the others only have "a couple" more ghosts to catch, only for many to show up.
- Insufferable Genius: Cyrus is a scientist, and he's snobbish, not liking the idea of a brilliant mind being an "exterminator".
- Labcoat of Science and Medicine: Egon wears a lab coat while working at Cyrus's lab.
- Manchild: According to Ray, poltergeists have a childish sense of humour.
- Mistaken for Undead:
- Inverted when Cyrus mistakes Slimer for a live cat.
- Subverted when it appears as though someone called the Ghostbusters mistaking some angry old ladies for ghosts, but it turns out there were ghosts there and the old ladies were just incidental.
- Neat Freak: Cyrus is displeased with the firehouse not being clean enough.
- Not So Stoic: Egon leaps when the Ghostbusters surprise him.
- Releasing from the Promise: Cyrus apologizes for how wrong he was about Egon's work and stops using his nephew's promise from years ago to make Egon work with him, sending him back to New York to continue his studies of ghosts.
- Right for the Wrong Reasons: Ray says that Egon caught a bunch of ghosts singlehandedly when trying to impress Cyrus. Cyrus is right that Ray isn't telling the truth, but thinks ghosts don't exist, when actually Ray wasn't lying, just exaggerating (since Egon didn't do it on his own).
- Say My Name: Janine angrily shouts, "SLIMER!" when he gets slime in her hair.
- Seen It All: Janine's only reaction to Cyrus accidentally opening the Containment Unit is to put down her clipboard and, expressionless and deadpan, say, "I really wish you hadn't done that, Dr. Spengler."
- Shared Family Quirks: Cyrus is a scientist just like his nephew.
- Skeptic No Longer: Cyrus initially disbelieved in ghosts, but was proven wrong.
- Slapstick: The poltergeists make Ray fall over.
- Tempting Fate: Cyrus is sure there aren't any ghosts at the mall, but there are.
- This Is Gonna Suck: When Cyrus opens the containment unit, Janine says in an annoyed way that she wished he hadn't done that.
- Unwitting Instigator of Doom: Cyrus accidentally frees the Stay Puft Marshmallow Man.
- What Does This Button Do?: Cyrus, in an attempt to find out what the containment unit does, starts randomly pressing buttons.
- You Are Fat: Exploited when Peter calls the Stay Puft Marshmallow Man "fat boy" to get his attention.
