This is one of the minigames you unlock later in the game at Episode 4. You will play this minigame as part of the story but that won't count towards the achievement so you will have to do this when you get to the beach at least.
Simply start the minigame by clicking on the Xylophone in your list of minigames in the bottom left corner of your screen, and then once it starts run up to each character and press X to freeze them. Freeze all 3 of them within 30 seconds to gain this achievement. Super easy.
You can follow my video guide below to see how it's done if needed: