In this scene, Penny bullies Sherman by calling him a dog. It's a great way to teach what bullying is and how it looks and feels to the person being bullied.
Sean bullies Annie in the cafeteria by making fun of her blind father and acting like he doesn't know that he's stealing her food. Annie defends herself by putting cake on his face and walks away.
Chuckie bikes with new friends to try and fit in with them. He falls into a mud pit, and all the kids think he is cool for being so brave. Chuckie realizes he does not want to hang out with these kids and goes back to his real friends.