I'm doing this from memory, so there may be inaccuracies or other silliness present.
Aaahh! Real Monsters centered around the life and studies of three monsters, Ickis (who vaguely resembled a rabbit), Krumm (a strange little semi-amorphous character with nearly deadly BO who holds his eyes in his hands), and Oblina (vaguely resembling a candy cane).
Ickis, Krumm, and Oblina live and study at the Monster Academy, located in the toxic depths of a large and active landfill. Their studies focus on the scaring of unsuspecting humans.
Their instructor, the Gromble, is a weird bluish creature with four feet, all in bright red high heels (an odd juxtaposition against his male figure). The Gromble has a VERY bad attitude. The main classroom of the academy is a large auditorium, with a special chair called the Viewfinder located at the back, which can be called upon to grasp a student with long steel arms and pass high voltage through their head, transforming them into a living LCD projector, thus allowing their recent scares to be viewed from memory (in the third person, oddly enough!). Each student monster has a large manual, containing a lot of information on the sacred art of terror.
The monsters travel from place to place via sewer. Anywhere that's accessible via toilet, manhole, or storm drain is fair game for their scaring exploits.
The students of the Academy live in fear of their horrible ogre in charge of discipline, the Snorch. The Snorch is accompanied by a large talking fly with feet, by the name of Zimbo. Although he works in a fully equipped torture chamber, his worst possible punishment is singing!
Ickis, Krumm, and Oblina have often been sent down to the lair of the Snorch, due to Ickis's habit of getting them into trouble. He has a quite oversized ego, yet, will shrink to a whining, quivering little mass whenever something goes wrong.
Aaahh! Real Monsters originally aired on Nickelodeon. I don't know if it's carried by any network at the moment.
Special thanks to Kyle3, who reminded me of the proper name of the Snorch's companion.