"Get up!" screamed Wilbur. "Stop acting like a spoiled child!"
Templeton grinned and lay still. (21.38-39)
When Wilbur realizes that Charlotte's egg sac needs to be fetched before the Zuckermans head back to their farm, he demands that Templeton help out. And what does Templeton want to do? Nothing at all, that's what. Check out how Wilbur takes charge here. It doesn't sound like he's an infant anymore. Instead of being the one acting like a child, now Wilbur is the one giving the orders.