The below description is taken from LEGO.com.
It must have been a magical unicorn! Yay!
Some people don’t believe in unicorns, but the Unicorn Girl is out to prove them wrong! Whether she’s prancing through mist-covered meadows, whinnying outside of windows and then running away giggling, or just throwing glitter everywhere, she’s determined to show the world that unicorns really exist.
The Unicorn Girl is always happy and optimistic. Nothing gets her down, not even people who say that she’s being silly and unicorns are only a myth. She just does something nice and thoughtful for them when they aren’t looking. Then, when they ask who did it, she smiles and says that it was a unicorn!