Coded for Elizabeth & Samuel's 10th Anniversary! Hooray!
Some bits of this came from other sources:
The Unicorns were adapted from the running horse animation at Wikipedia — this goes back to Eadweard Muybridge!
The sounds all originated from Orange Free Sounds (Horse Neigh, Hit, Ta-da, Fireworks, and Sad Trombone). They were tweaked as needed.
Audio icons adapted from Wikimedia.