What is the difference between “put on” and “wear”?
"Put on" means that you are currently dressing yourself. To "wear" something means to already be dressed in a piece of clothing and to currently dress yourself. To avoid confusion, Gru tells the girls to put on their PJs, he is telling them that they need to get dressed into clothes that they can sleep in. Here are a couple of examples of both: Please put on your swimsuit before we go to the pool. I am wearing a sweater because it is so cold today.