How did all mighty King Julien get to know those weird animals from that New York land?

The day Alex and his friends came to Madagascar, King Julien and his subjects were enjoying their party celebrating Clover's wedding when it was invaded by the fossa. When the fossa was scared off by Alex, King Julien and his people were hiding in the trees and saw this scene, thinking Alex and his friends were aliens until they passed his test when he kicked Mort towards them. He thinks them to be giant pansies and he thinks to present himself as the king of the lemurs with the other lemurs appearing from where they were hiding. When Alex asked where the people were, Julien pointed to a skeleton of a man caught in a parachute hanging from a tree. King Julien was immediately impressed with how Alex handled the fossa, not noticing why the Fossa were scared unlike Maurice, and began to conjure up a plan. Maurice is to show characteristics of a reasonable advisor which was shown in AHKJ. He continuously suspects him and goes to the extend and asks Alex about his "big teeth."

Later that night, King Julien had a meeting of the lemurs and other creatures of the jungle in the plane. Julien insisted that if they could make friends with Alex and his friends, the Fossa would be scared away for good. Maurice was skeptical about this plan since he had become suspicious of Alex due to Alex’s predatory nature beginning to show, but King Julien insisted that being king, his ideas were the best, so Maurice reluctantly agreed to this but still held onto his suspicions. Though his plan was a risky one, he did this protect his people from the dreaded foosa. Though he becomes self-obsessed and ignores Maurice's warning, the audience sees that he only wants his peoples' safety and shows qualities of a good leader.

The next morning, King Julien and the lemurs welcome Alex and the gang into their kingdom with open arms. However, during a performance, Alex reverts to primal hunting instincts and bites Marty. Maurice informs them that Alex bit Marty because lions are carnivores and eat meat, particularly steak, which comes from other animals. Realizing that Maurice was right and admitting that his plan failed, King Julien banishes Alex to the predator side of the island with the rest of the Fossa. Alex shows his predatory characteristics and chases Marty. King Julien and Maurice are on a coconut tree and Maurice hits Alex with a coconut. King Julien praises him here.

When the penguins and the chimps arrive on the ship after a brief stay in the Antarctica, they come and decides to help Marty. They fight off the foosa to save Marty. After Alex has shown the foosa how savage he is, he hugs his friends. At this moment, King Julien appears with Maurice and asks Maurice to give him some love and hugs Maurice. Later, they help Alex control his cravings by feeding him sushi, which he actually loves. At this moment, King Julien offers Mort as "Plan B", hoping that Alex would eat Mort. Mort laughs at this moment. As thanks for saving them from the fossa, King Julien gifted Alex the sacred crown used by the kings of the Julien lineage; however, he had already made himself a brand new, bigger, better one, with a gecko named Stevie on it, so as to prevent Alex from returning the original. Despite enjoying Madagascar, Alex, Marty, Melman, Gloria, Phil, and Mason decided to go back to New York on the ship. Unfortunately, Skipper chose not to tell them that the ship is out of fuel, leaving them stranded on the island.