Aaahh!!! Real Monsters (1994)

Deep beneath a smelly garbage dump, a generation of promising young monsters is growing up. Ickis, Oblina and Krumm are students in one of the world's most elite monster academies, where they're studying the fine art of scaring the daylights out of people. Learning to be a top monster from their strict headmaster, the Gromble, is hard work, so the trio relies on each other's help in dealing with the day-to-day trials of monsterdom. Despite their shortcomings--Ickis' insecurities, Oblina's bad temper and Krumm's tendency to be a slacker--their friendship gets them through their hideous homework and horrendous adolescence.