A perfect example from this book is Templeton the rat. Yes, he ends up helping Charlotte and Wilbur many times but the way the author writes it, it’s obvious he doesn’t care, really, about anyone but himself. This becomes abundantly clear at the end of the book. He does his final good deed for Wilbur- taking down Charlotte’s egg sac to bring back to the barn- but he demanded something out of it; this being the first to eat out of Wilbur’s trough. This small detail was the turning point. It's now apparent that Templeton is a dreadful character.
But I feel like the author needed to write him like this. This is all children know- there are good people and then there are bad. Without it, they would be lost; it’s like food to them.