It's a sleepover at the castle and Unikitty and Puppycorn want to stay up all night, believing something magical must happen if you stay up long enough. At first the friends are game to stay up all night, but as they fall asleep one by one, Unikitty worries they won't make it! How far will she and her bro go to stay awake, and will they discover the secret reason people are supposed to go to bed when the Sandman shows up?