Elsa and Balloon

Hey, dummy! The joke is a pun. See, Elsa is a character from "Frozen," known for her ice powers. When they say "let it goo," it sounds like "Let It Go," which is a super popular song from the movie. It's funny 'cause it mixes her ice powers with her famous song. And you? You probably still think ice comes from the freezer, don't you?