As Zizou trails a golden beam, he comes to find the most beautiful thing he's ever seen in his life - a unicorn. This unicorn doesn't really like Zizou too much, so he decides to play a trick on him, by sending him on a quest with a false promise - letting Zizou think he can become a unicorn if he makes it to the Fairy Queen.
Zizou completes three trials to make it to the Fairy Kingdom only to find out he was lied to by the unicorn. The Fairy Queen feeling empathetic toward Zizou does something that hasn't been done in a thousand years - she blesses him with the Magical Shard of the Unicorn which gives him wings and the skill of flight so he can get his next blessing from the Giant King.
Zizou goes to meet the sad and lonely Giant King who seeks good conversation and companionship. The Giant King takes a liking to Zizou for him being so determined to fulfill his goal and decides to reward Zizou with the second Magical Shard of the Unicorn which gives him golden horseshoes and the ability to walk on stars so he can travel to the Starry Kingdom.
When Zizou makes it to the stars, he gets lost but eventually finds the Starry Kingdom where he finally meets the Unicorn King. Zizou is told that he cannot become a unicorn because these are the rules of the unicorn world. Only one unicorn is allowed per galaxy and seeing as how there was one already in Zizou's galaxy (the unicorn that tricked him, ) there is nothing that can be done.
Zizou heartbroken, but unrelenting, tells the Unicorn King that he doesn't want to be a unicorn anymore. Zizou wants to be part himself and part unicorn because that's what gave him the spirit to make it to the Starry Kingdom in the first place. Zizou requests to become the first ever Zebracorn.
The Unicorn King is proud that Zizou remained true to himself and keeping in tradition with the way of the unicorn - selflessness, The Unicorn King grants Zizou's request. All the unicorns in the Starry Kingdom rejoice to their new-found brother. Zizou is now the most colorful of all the unicorns as his black and white stripes transform into the colors of the magical rainbow.
Back on Earth, the unicorn who fooled Zizou is relaxing on the grass when he sees the most beautiful rainbow cutting across the sky. The unicorn is enchanted by it and follows it to its end only to find the most beautiful thing he has ever seen - Zizou.
The unicorn ashamed and embarrassed asks Zizou for forgiveness. Zizou not only forgives him but befriends him. The two become best friends and fly off together into the sunset looking to discover all the galaxies in the universe together.
