When you enter the room, you can click on Sophie or the arrow on the right of the room to play a minigame. In the minigame, you are suppose to catch "dreams". The minigame is similar to catching the honey pots in Mythology Island. You have 3 minuets to find all 10 dreams.
When you complete the game, you are awarded two prizes. One is the Giant Costume which is a costume of BFG. The other is a Stomp Power which is activated by pressing the space and your poptropican will stomp causing the screen to shake.
If you are having trouble with the minigame, below is a video tutorial of it!
Enjoy the prizes and minigame while they last!