The show focuses on three young monsters — Ickis, Oblina and Krumm — who attend an institute for monsters under a city dump and learn to frighten humans. Many of the episodes revolve around them making it to the surface in order to perform "scares" as class assignments.
The show is set in New York City, demonstrated throughout the series by the presences of the Empire State Building and "IND Subway". The dump the monsters inhabit is implied to be Fresh Kills Landfill, but never explicitly named in the series.
Ickis - Ickis is a small red monster who, due to his large ears, is often confused with a rabbit. He is the son of Slickis, a famous scarer. He seems the most skiddish of the monsters but is also a capable leader. Ickis loom (growing in size) to scare and comes from a long line of loomers.
Oblina - Oblina comes from a wealthy monster family, and is considered by The Gromble to be his best student. She is shaped like a black-and-white, upside-down candy cane, resembling a banded sea krait. One of her favorite methods of scaring humans is reaching within herself and pulling out her internal organs, and she has considerable talent for shapeshifting into various terrifying forms. She also has a talent for inducing nightmares in humans, by sticking her finger in their ear and tickling their brains while they sleep.
Krumm - Like the rest of his family, his eyeballs are not attached to his body, and are usually seen carried in his hands; if he requires the use of both hands, he can carry them in his mouth. His most valuable tool in scaring is his overwhelming armpit stench as well as using his eyeballs.