Listen to article(1 minute)They are on Walmart shelves, candy wrappers and dog costumes. They are in theme parks in Florida and Southern California. They have appeared on Amazon.com Inc. delivery boxes, chickpea snack bags and Tic-Tac containers. They have made cameos in countless Facebook memes, standing in for fans who want to express every conceivable emotion—from back-to-school excitement to calls to indict former President Donald Trump. People have them tattooed on their bodies. Others coat themselves in yellow makeup to dress up like them.