Hooray! Hooray! It's Unicorn Day! When unicorns come out to play. The most important rule of Unicorn Day is to have fun, fun, fun! The unicorns are celebrating their favorite day of the year, complete with rainbows, cupcakes, butterflies, and all sorts of joyful things. But when it's revealed there's an impostor in their midst, the party comes to a screeching halt... Will the unicorns welcome all and continue their fun in all its glittery glory? A clever, colorful, and over-the-top picture book about unicorns, celebrations, and most importantly, friendship.