Maurice is the advisor of King Julien and raised said Lemur from a baby after the queen died. He's the brains of the Lemurs and was the only one to think there was a reason to fear Alex as the Fossa did. He leaves Madagascar with King Julien and Mort.
Madagascar: Escape 2 Africa
Maurice joins King Julien and Mort in leaving Madagascar. He didn't play much of a role except for aiding King Julien in his hair-brained scheme in sacrificing Melman into a volcano to bring water to the dehydrated creatures of Africa.
Madagascar 3: Europe's Most Wanted
By Madagascar 3, it seems Maurice feels exasperated and stifled by King Julien. When King Julien fell off the edge of a building in Monte Carlo, he was the only one who started to smile, looking hopeful. When the King survived, he switched back, looking disappointed.
In the circus, he and Mort took on the act of ribbon dancing.
The Penguins of Madagascar series
In the Penguins' spinoff series, Maurice is a main character, especially in the pilot episode 'Gone in a Flash', where he gets aggravated by King Julien's stupidity, and when Maurice ends up missing after King Julien accidentally takes a picture of him in a camera, thinking he trapped him inside as 'punishment for questioning his authority', he ended up in a junkyard and at first refused to leave when the Penguins attempted to rescue him, but then he ended up being rescued anyway. Since then, he has been a supporting character in the series, helping the Penguins and King Julien with whatever trouble is going on.
All Hail King Julien
Maurice was King Julien's advisor, he still goes on adventures with him.
Even if he isn't the smartest animal in the zoo, Maurice is still much smarter than both King Julien and Mort combined. He does not share the other two lemurs' bad cases of the "stupids". He is more grounded then any of the other lemurs or penguins. He is very loyal to King Julien, and is like an older brother to Mort. This was shown in Right Hand Man when he helped the penguins stop Clemson from getting rid of Julien, and in Operation: Plush and Cover when he was incredibly happy when the penguins rescued Mort.
Role in the series
Maurice is a member of The Jungle Crew just like King Julien and Mort. He mainly has to watch over the both of them so they don't cause any trouble, and occasionally has to aid the Shell Lodgers in their missions when the danger threatens their homes.