The Rice University Neologisms Database

Those for whom a baby-sitter is hired. When referring to himself in the third person, Calvin needed a word which referred to the charges of the baby-sitter. A possible past-tense for “baby-sit” is “baby-sat”, and so the essence of Calvin’s statement is “The revenge of those who are being baby-sat” or “The revenge of those over whom the baby-sitter is in charge.” Both of those statements sound rather adult, and sound like they come from a veteran speaker of English, and a child is much more likely to create a new word which sounds right to him.