While a monster emerges from some water and jumps into the Atlantic Ocean, the Ghostbusters are at a fancy party at a hotel. They are on the trail of an Irish ghost, and Mayor Lenny is throwing the party to celebrate St. Patrick's Eve, having invited every important Irishman in New York. The Ghostbusters catch the ghost, but then a woman enters and screams at the damage, and Peter fires at her, mistaking her for another ghost.
This gets all of them arrested, and they're sent to prison, where it's revealed that the woman survived, but she was Lenny's wife. Lt. Frump laughs at them, but the deputy police chief, O'Malley, offers to let them go if they do something for him: a long time ago, his ancestors stole gold from a leprechaun, who cursed them so that whenever St. Patrick's Day falls on a full moon, the monster seen at the beginning of the episode (which is called the Bog Hound) abducts the head of the clan, which he is, showing them a piece of Bog Hound fur to prove it. The Ghostbusters are doubtful, but they accept, wanting to get out of jail.
The Bog Hound arrives in New York, and O'Malley tells the Ghostbusters that the way to deal with the Bog Hound is with a four-leafed clover. Egon, however, thinks this probably wouldn't work and tries to trap the Bog Hound instead, but when he tries at the zoo, he fails and narrowly escapes. Meanwhile, the other Ghostbusters search for four-leafed clovers, and after a few mishaps, Peter finds one at the Botanical Gardens. However, Slimer eats the clover, so everyone decides that trapping the Bog Hound would be easier.
They pursue the Hound at the St. Patrick's Day parade and keep shooting at it, but miss. Then, the Bog Hound chases Peter up a pole, and he lands in the laps of Mayor Lenny and his wife. Meanwhile, Winston and Ray's packs get destroyed by a float, so the Bog Hound corners them and O'Malley. Peter takes a clover from Lenny's wife's corsage and tries it on the Bog Hound but it doesn't work since it's a plastic clover. It chases Peter, but luckily, Egon traps it, and the directors of the parade declare the Ghostbusters "honorary Irishmen". They are then awarded medals by Lenny's wife, who gets her revenge on Peter by pinning him.
This episode provides examples of
- Animal Jingoism: Zigzagged. The Bog Hound chases big cats, but also humans.
- Anthropomorphic Food: Invoked when the ghost possesses a turkey.
- Arbitrary Skepticism: The Ghostbusters, especially Egon, are doubtful of O'Malley's story (especially the part about the four-leafed clover being the solution) even though, as they even point out, they deal with the supernatural all the time.
- Brought to You by the Letter "S": A boy in the parade has an "S" on his shirt.
- Call a Smeerp a "Rabbit": Played with — the Bog Hound is called a "hound" despite not looking very doglike, yet it does behave a lot like a dog.
- Cat Up a Tree: Parodied — the Bog Hound chases big cats, like lions, up a tree.
- Contrived Clumsiness: Lenny's wife sticks him with pins, intentionally but she pretends she was just being clumsy.
- Curse: The O'Malleys got cursed as a result of an ancestor stealing gold from a leprechaun, leading to the Bog Hound going after whoever's the head of the clan.
- Did You Just Flip Off Cthulhu?:
- In the zoo scene, Egon teases the Bog Hound and calls it Fido.
- Later on, Peter yells at and taunts the Bog Hound (at one point, calling it Four-Eyes) to distract it from Ray, Winston, and O'Malley.
- Evil Laugh: The Irish ghost chuckles evilly twice.
- Evil Smells Bad: Justified for the Bog Hound, who smells like a wet dog because it's a hound and it had just swum the Atlantic Ocean.
- Extra Eyes: The Bog Hound has four eyes.
- Flat Joy: Janine says, "Hooray" in a deadpan voice when Peter declares he's found the clover, since she doesn't know why it's meant to be good.
- Glass-Shattering Sound: The Bog Hound's howl breaks a few windows.
- Go Fetch: Egon distracts the Bog Hound by throwing a stick.
- Green and Mean: The evil Bog Hound is a murky green colour.
- Hellhound: The Bog Hound is a vicious, doglike demon.
- Hope Spot: Peter finds a four-leafed clover... which is then eaten by Slimer.
- I Meant to Do That: In the beginning scene, Peter lies that he meant to miss the ghost.
- Instantly Proven Wrong: Upon climbing the tree, Egon says that it's safe up there... and then notices it's full of big cats.
- Laughably Evil: Downplayed for the Bog Hound, who's a legitimate threat, but also does goofy doglike things like chasing sticks.
- Leprechaun: The catalyst for the curse was an O'Malley stealing gold from a leprechaun.
- Lightmare Fuel: There's a demonic creature that's perfectly able to kill... yet, it behaves like a domestic dog.
- Mistaken for Racist: When Ray explains to the police officer that he's looking for a four-leafed clover to kill a Bog Hound that was part of a leprechaun's curse, the police officer thinks Ray's mocking him for being Irish.
- Mistaken for Undead: Peter mistakes Lenny's wife for a ghost because she was far away, screamed, was wearing green, and was pale.
- Needle in a Stack of Needles: Ray's place he chooses to search for a four-leafed clover is in a patch of clovers.
- Nice Kitty...: In the zoo scene, Egon nervously tries not to provoke the vicious animals by referring to the big cats as "nice kitties" and the Bog Hound as a "good doggy".
- Not So Stoic: Egon looks visibly fearful when being chased by the Bog Hound.
- Pun:
- Egon tells the Bog Hound, who's a doglike creature and is near a tree, that it's "barking up the wrong tree".
- Peter says that he needs to "see a man about a dog", referring to saving Winston, Ray, and O'Malley from the Bog Hound.
- Red Eyes, Take Warning: Both supernatural villains, the Bog Hound and the Irish ghost, have red eyes.
- Revenge: Played for Laughs when Lenny's wife gets back at Peter for nearly killing him by sticking him with pins.
- Speak in Unison:
- Winston, Ray, and Egon say, "Uh-oh!" in unison when Peter accidentally fires at Lenny's wife.
- The Ghostbusters say in unison, "Let me guess — you're the head of the O'Malley clan?".
- Stink Snub: When an old man smells the Bog Hound, he says to the guy next to him, "Have you taken a bath lately? Because something smells an awful lot like wet dog!".
- Stock Animal Food: Egon teases the Bog Hound by calling it "Fido".
- St. Patrick's Day Episode: Played for Horror — it's St. Patrick's Day, which (in addition to a full moon) causes a monster to attack as part of a family curse.
- Time Travel: Discussed when Egon wants to go back in time to meet his fish ancestors.
- Wolves Always Howl at the Moon: Played with — the Bog Hound, a doglike monster, howls at the moon.
