Definitely not. The movie is purely imaginative and doesn't draw from real-life events. It's designed to take viewers on a fictional adventure with made-up characters and situations.
Well, it could be about two children who are mischievous and their real - life adventures are turned into this story. Maybe they got into all sorts of trouble around the house or in their neighborhood.
The '2 little monsters based on true story' could refer to two animals that were acting in an unusual or naughty way. For example, two raccoons that kept getting into people's garbage cans in a neighborhood. People might call them little monsters in a light - hearted way because it was a true - life nuisance they were facing.