Aaahh!!! Real Monsters was a cartoon about monsters in training, that originally ran on Nickelodeon from October 29, 1994 – November 16, 1997 and was rerun on Nicktoons up until 2006. It was Developed by Klasky Csupo, which also produced the animated shows Rugrats and Duckman. Real Monsters focuses on the adventures of three young monsters: Ickis, Oblina and Krumm. The three of them are attending an institute for monsters where they are learning the important monster killed of frightening humans. It was a great example of the creative powerhouse that was 1990s Nickelodeon and is worth checking out if you have not seen it or just want to get reacquainted with a classic show.
Oh and here, for your online viewing pleasure is episode 1 of the show: