The animals are bribed to celebrate King Julien Day with the promise of receiving a piñata as a reward, but the day itself is only fun for King Julien.
King Julien announces that tomorrow is 15th day of the month and the biggest holiday of the year, which is "King Julien Day". Maurice tries to get everyone to remember King Julien day and celebration of it, claiming that if they forget, Julien will go insane and attack them physically and/or mentally (or, what they say, "freak").
Despite the proposition of receiving a piñata full of candy that Mort and Maurice had snatched from a rained out birthday party, but Skipper refuses to celebrate as he prefers to spend the day carrying out scheduled maintenance on the penguins' headquarters (Because you can't go about rescheduling scheduled maintenance that's been scheduled, right on the schedule).
The other animals go along and celebrate King Julien day with the sole purpose of obtaining the candy inside of the piñata. They bask in his glory, limbo, let Julien throw fruit at them, and have a cake bake off in his honor. Mort trips while delivering the winning cake as it starts to soar through the air and it lands on Skipper's head.
This is the final straw for Skipper who comes over to the lemur habitat to tell Julien that there's no such thing as King Julien Day, which causes Julien to almost freak but he calmed down when he realized Skipper had brought the winning cake. Maurice brings out the piñata but Julien thinks it's just a paper horse that belongs to him. Julien names the piñata "Bob" and walks off with him. However, he returns and Kowalski, Marlene and the other animals who came to the party still receive candy because there is still the "Traditional Sharing of the Sweets", as an important part of King Julien Day.